Pondicherry University Entrance Exam Question Papers qn5c

x n y

(Dl

(A)

X

X

!Y

x t. y

14.

The Boolean function F= 2: (0,1,2,8,10,11,14,15) gives the minimized function (A) w'x'y' + x'Z: + w'y' (B) w'x'y' + xz+ w'y' (C) w'x'y' + x'z' + wy (D) wx'y' + x'z' + w'y'

15.

The circuit below was designed to implement F AB'D + BC'D' + BCD, but it is not working properly. The input wires to gates 1,2 and 3 are so tightly packed, it would take you a while to trace them all MESS back to see whether inputs are correct. It Of would be mce to only have to trace WIRES whichever one is incorrectly wired. \ilfhen A = B =0 and C =D = 1, the inputs and Doutputs of gate 4 are as shown. Then, which of the gates either is connected incorrectly or is malfunctioning

=

(A) (C)

the

logic

equation

Gate 2 (D) Gate 4

(B)

Gate l Gate 3

3

304

16.

17.

18.

Saturated logic circuits have inherently: (A) Short satura t.ion delay time (Cl Higher power speed CMOS family uses only: (A) MOSFETs and s (C) NMOS circuit

(B)

Low switching speed (D) Lower noise margin

(B) (D)

MOSFETs Bipolar transistor

TIL family has: (A) Less noise margin (B)

(C) (D)

Smaller speed Power dissipation of 100 mw at 25"C Fan-out of 50

19.

The process used in fabricating the components of monolithic ICs is: (A) Diffusion (B) Evaporation (C) Sputtering (D) Oxidation

20.

How many layers of different materials are in the basic structure of IC: (A)

21.

1

(B)

(C)

2

3

(D)

4

The discrete-time signal x(n)=(-1)• is periodic with fundamental period: (A)

6

(B)

4

(C)

2

(D) 0

22.

Two sequences x1(n) and x2(n) are related by x2(n) = Xl(-n).ln the Z-domain their ROC's are : (A) The same (B) Reciprocal of each other (D) Complements of each other (C) Negative of each other

23.

The unit impulse response of a linear time invariant system is the unit step function u(t). For t>O, the response of the system to an excitation e·at u(t),a>Owill be: (A) ae~" (B) 1-€-•'/a (C) a(l-e-•') (D) 1--il...,

24.

The auto-correlation function of a rectangular pulse of duration Tis:

304

(A) (B)

A rectangular pulse of duration T A rectangular pulse of duration 2T

(C) (D)

A triangular pulse of duration T A triangular pulse of duration 2T

4

=

25.

The Fourier transform of a rectangular pulse existing between t -T/2 tot= T/2 is (A) A Sine squared function (B) A Sine function (C) A Sine squared function (D) A Sine function

26.

If Rl is the region of convergence of x(n) and R2 is the region of convergence of y(n),then the region of convergence ofx(n) convoluted y(n) is (A) Rl+R2 (B) Rl- R2 (C) RlnR2 (D) RlvR2

27.

The continuous time system described by y(~)=x(t2) is: (A) Causal, linear and time varying (B) Causal. non-linear and time varying (C) Non causal, non-linear and time invariant (D) Non causal, linear and time invariant

28.

A band signal extends from 1 KHz to 2KHz. The minimum sampling frequency needed to retain all information in the sampled signal is: (A) 1 KHz (B) 2 KHz (C) 3KHz (D) 4 KHz

29.

The system characterized by the equation y(t) = a.X.(t) +b is: (A) Linear for any value of b (B) Linear if b > 0 (C) Linear if b < 0 (D) Non-linear

30.

X(n)= al•l, Ia I
31.

The "Superposition theorem" is essentially based on the concept of (A) Duality (B) Linearity (C)

32.

Reciprocity

(D)

Non-linearity

The Q· factor of a coil is given by (A) Its power factor cos j. (B) Ratio of ma..x. energy stored & energy dissipated per cycle. (C) Reciprocal of its power factor. (D)

Ratio R/Z. 5

304

33.

34.

In an R- L -C circuit, the phase of the cunent with respect to the circuit voltage will be (A)

Leading

(B)

Same

(C)

Lagging

(D)

Depends upon the value of Land C

The frequency of DC supply is (A)

35.

37.

38.

39.

304

(C)

50 Hz

Power improvement Voltage improvement

(B)

Current improvement

(D)

100Hz

(D) Power factor improvement

(A)

RIZ

(B)

2 n fUR

(C)

2 n fRL

(D)

UR

In India, electrical power is transmitted by (A)

1 -phase a.c. system

(B)

3-wire d.c. system

(C)

3-phase 3-wire a.c. system

(D)

2-wire d.c. system

A network that does not have either voltage or current sources is called (A)

Active network

(B)

ive network

(C)

Resistive network

(D)

Dummy network

The Power· factor at resonance in R· L-C circuit is (B) Unity (A) Zero 0.5 lagging

(D)

0.5 leading

Which of the following bulbs will have the least resistance? (A) (C)

41.

16 Hz

Q factor of an inductive coil is given by

(C) 40.

(B)

Static Capacitors are used for (A) (C)

36.

Zero

220 V, 60 W 115 V, 60 W

220 V, 100 W (D) 115 V, 100 W (B)

The temperature in a auditorium is given by T=2x2 +y2 -2z 2• A mosquito located at (2, 2, 1) in the auditorium desires to fly in such a direction that it will get warm as soon as possible. The direction, in that it must fly is (A)

8tt. + 8uy- 4u,

(B)

2u.+ 2uy-lu,

(C)

4u, + 4u,.- 4u,

(D)

- (2u, + 2u,.- 1u,)

6

' 12.

The phasor magnetic field intensity for a tOO MHz uniform plane Wll\'e propagating m a certain lossless mntenal is (6u,- j5u, ~-t»• A i m.'fhe phase velocity Vp 1s (A) (C)

43 x 106 m/ ~ 1.4 x 1OB m/ s

(B)

2.2 x 107 m/ s (D) None of the above

IS filled with a polyethylene (c, = 2. 25) and oa>erates at 24 GHz. The cutoff frequency of a certain mode is 16 GHz. The intrinsic 1mpedance of this mode is (A) 2248 Q {B) 337.2 Q (C) 421.4 Q (Dl 632.2 Q

13.

A rectangular wavegu1de

44 .

The air filled cavity resonator has dime nsion a 3 em, b resonant frequency for Lhe TM11o mode is (A) 5 GHz (B) 6.4 GHz (C) 16.2 GHz (D) 9 GHz

45.

1\,·o 1dentical rectangular waveguide are jomed end to end where a= Zb. One guide is !Ill' filled and other is filled with a lossless dielectric of c,. It is found that up to a certain frequency single mode opera tion can be simultaneously ensured m both guide. For this frequency range, the maximum allowable value of c, is

=

(A)

46.

47.

(B)

2

(C)

1

=2 em, ( = 4 em. The

(D) 6

A parallel-plate guide operates in the 'l'EM moue only over the frequency rangeO < f < 3GHz. The dielectric between the plates is Teflon (c, 2.1) . The maximum allowable plate separation b IS (A) 3.4 em (B) 1.8 em (C) 4.3 em {D) 8.6 em

=

A Hertizian dipole at the origin in free s pace has dl = 10 em and I =20 cos (2n xlO' t) at the dista nt point (100, 0, 0) is

A. The

1'4

(A)

0.252 V/ m

(B)

0.126 VIm

(C)

0.04 V/ m

(D)

0.08 V/ m

48.

An antenna can be modeled as an electric d1pole of length 4 m at 3 MHz. If current is uniform over its length, then radiation resistance of the antenna is (A) 1974 Q (B) 1263 Q (C) 2.186 Q {D) 2.693 Q

49.

An antenna has directivity of 100 and operates at 150 MHz. The maximum effective aperture is (A) 31.8 m 2 (B) 62.4 m 2 (C) 26.4 m2 (D) 13.2 mt 7

304

50.

An antenna is desired to operate on a frequency of 40 MHz whose quality factor is 50. The bandwidth of antenna is (A) 5.03 MHz (B) 800kHz (C) 127kHz (D) None of the above

51.

The function of an ampliLude limiter in an FM receiver is (A) To eliminate any change in amplitude of received FM signal (B) To reduce amplitude of the signal to suit IF amplifier (C) To amplify low frequency signals (D) None of these

52.

In FM, the noise can be further decreases by (A) Decreasing deviation (B) Increasing deviation (C) Keeping deviation constant (D) None of these

53.

In AM, if modulation index is more than 100%, then (A) Power of the wave increases (B) Efficiency of transmission increases (C) The wave gets distorted (D) Band,vidth increases

54.

A radio receiver is tuned to 710 KHz and its oscillator frequency is 885 KHZ. The image frequency would be (A) 1420KHz (B) 1770KHz (C) 1050 I
55.

The paddcrs in receivers is 'Used to improve (A) Tracking (B) Image frequency rejection (C) Noise reduction (D) Sensitivity

56.

Which of the following is not uniformly distributed over all frequencies? (B) Flicker noise (A) White noise (C) Short noise (D) Thermal noise

57.

The function of baffles in speaker system is (A) To allow high frequencies to (B) To provide stability to the speaker (C) To avoid cancellation of compression and ratification of air (D) To produce echo effect

304

8

58.

An FM wave is represented by (e= 12sin•6x lOE r+Ssil(1150t!], the modulating index is (B) 12 (A) 6 (D) 5 (C) 10

59.

Frequency and phase modulations differ in (A) Different definitions of the modulation indices (B) Their actual waveform (C) Compatibility towards each other (D) All of these

60.

Telephone receiver employs (A) Condenser Microphone (C) Crystal Microphone

(B)

The Nyquist rate of a signal is (A) f., .. sample/sec (C) 1/ f., .. samples/sec

(B)

61.

62.

(D)

{D)

Carbon Microphone None of these

2 fmax samples/sec 1/2 fmax samples/sec

A signal of maximum frequency of 8KHz is sampled at Nyquist rate. The time intervals between two successive samples will be (A) 125 ).!SeC (B) 1250 ).!SeC (C)

zero

(D)

62.5 J.lSec

63.

A communication channel has bandwidth of 5 KHz and if signal-to-noise ratio is 5, the corresponding channel capacity will be (A) 18000 bits/sec (B) 4000 bits/sec (C) 1500 bits/sec (D) 1000 bits/sec

64.

In PCM, for 128 standard quantizing levels, the maximum error will be (A) 11128 of the total amplitude range (B) 11256 of the total amplitude range (C) 1/64 of the total amplitude range (D) '!. of the total amplitude range

65.

Satellite tracking stations are located in remote areas in order to minimse the effect of (A) Solar noise (B) Cosmic noise (C) Man-made noise (D) Thermal noise 9

304

66.

67.

68.

69.

70.

71.

72.

The entropy rate of a communication system is (A)

Total information transmitted

(B)

Maximum of Information

(C)

Average information

(D)

Tnformation rate

Which of the following statement about PCM is incorrect? (A)

PCM requires small bandwidth

(B)

PCM is a digital system

(C)

PCM is inherently most noise resistant

(D)

All of these

In differential PSK (A)

Power requirement is twice that is coherent detection

(B)

Noise excursions cancel in the comparison process

(C)

Above both are correct

(D)

None of these

In digital transmission, impulse noise can cause loss of (A)

Digital signal

(B)

SIN ratio

(C)

Synchronization

(D)

All of these

For a periodic function, the spectral density and the auto-correlation functions are (A)

Z-transform

(B)

Laplace transform pair

(C)

One and the same thing

(D)

Fourier transform pair

The line equalizers are employed in modems to correct (A)

Freq ucncy variations

(B)

Phase variations

(C)

Amplitude variations

(D)

None of these

The number of special function s in 8051 microcontroller is (A)

73.

(B)

41

(C)

51

(D)

31

The number of memory cycles required to execute the following 8085 instruction LOA 3000H would be (A)

304

21

2

(B)

(C)

4

10

3

(D)

5

74.

In 8085, TRAP is (A) Always mask able (B) Cannot interrupt a service sub-routine (C) Used for catastrophic events like temporary power failure (D) Lowest priority interrupts

75.

The mnemonics used in writing a program is called (A) Object program (B) Fetch cycle (C) Micro-instructions (D) Assembly Language

76.

The data pointer of 8051 microcontrollcr is (A) 16 bit (B) 8 bit (C)

32 bit

(D)

64 bit

77.

Interaction between a U and a peripheral device that takes place during an I/0 operation is known as (B) Handshaking (A) Flagging (D)' Subroutine (C) Relocating

78.

The first machine cycle of an instruction is always (A) A memory read cycle (B) A memory write cycle (C) Fetch cycle (D) A UO read cycle

79.

How (A) (B) (C) (D)

80.

An interrupt service request is service (A) After the execution of the current instructions is completed (B) Immediately on receipt of request (C) At the end of the current machine cycle (D) None of these

81.

An organ pipe which is open at both ends resonates at its fundamental frequency. Neglecting any end effects, what wavelength is formed by this pipe in this mode of vibration if the pipe is 2 meters long? (A) 2 meters (B) 4 meters (D) 8 metera (C) 6 meters

many and what are the machine cycles needed for execution of XTHL? l,Fetch 3,Fetch,Memory read and write 4, Fetch,2 Memory read and 2 Memory write 5,Fetch,2 Memory read and 2 Memory write

11

304

82.

83.

84.

85.

86.

304

According to the second law of thermodynamics, energy tends to become more and more unavailable for conversion from: (A)

Thermal to kinetic energy

(B)

Kinetic to thermal energy

(C)

Thermal to mechanical energy

(D)

Mechanical to thermal energy

An ice skater is rotating with her arms extended. When she pulls in her arms her rate of rotation increases. Which of the following statemen ts dealing with the process is TRUE? (A)

Her moment of inertia is increased.

(B)

Kinetic energy is conserved.

(C)

The skater does work when pulling in her arms.

(D)

Angular momentum is increased

The temperature of a gas measures the: (A)

number of calories of heat present

(B)

average kinetic energy of the particles in the gas

(C)

exact number of particles in t he gas

(D)

potential energy of the gas

It is a very hot day. You arc in a special kitchen, in that there are no exits and the walls of this kitchen are thermally very well insulated. If you open the refrigerator door, the room will eventually: (A)

Cool off

(B)

Remain the same

(C)

Heat up

(D)

None of the above

Consider two water drops at a temperature T. These drops are NOT allowed to exchange energy with their environment. These two drops collide and combine. How does the temperature of these drops change when they combine? Does it? (A)

Decrease

(B)

Remain the same

(C)

Increase

(D)

lfl'

12

87.

88.

89.

90.

91.

Which of the following quantities has the GREATEST influence on the overall efficiency of a conventional (Rankine cycle) electric generating station burning fossil fuels? (A)

Steam temperatme at the steam turbine inlet

(B)

Net heating value of the fuel

(C)

Steam pressure at the steam turbine inlet

(D)

Pounds of ash and sulfur per pound of fuel

The theory which ascribes wave-like properties to particles is called; (A)

General relativity

(B)

Quantum mechanics

(C)

Special relativity

(D)

Classical mechanics

Imagine that a 20 mile diameter hole is bored along the diameter of the Earth extending from the North Pole to the South Pole, that all air and gases are pumped out of this hole, and that the temperature throughout this hole is maintained at 300 Kelvins. A boy throws a ping pong ball into this hole. The ping pong ball would: (A)

Fall to the center of the Earth and remain forever suspended there.

(B)

Fall to the opposite side of the Earth's surface and remain forever suspended there.

(C)

Forever oscillate in simple harmonic motion along the hole between the loci of the hole with the opposite surfaces of the Earth.

(D)

None of the above.

When a liquid moves through a pipe having a varying diameter, the pressure against the inside walls of the pipe will be: (A)

the same throughout

(B)

lowest where the diameter is smallest

(C)

lowest where the diameter is largest

(D)

lowest where the velocity of flow is lowest

A fair coin is to be tossed 8 times. What is the probability that more of the tosses will result in heads than will result in tails? (A)

92.

23/64

(B)

(C)

113

87/256

(D) 93/256

How many integers from 0 to 1000 are divisible by 30 but not by 16? (A)

29

(B)

(C)

30

13

31

(D)

32

304

93.

Let v, = (1,1,0,1), v2 = (1,1,1,1), V3 = (4,4,1,1) and V< = (1,0,0,1) be elements ofR• . The set of vectors { v1, v2, v3, v4 } is (A) Linearly independent (B) Linearly dependent (D) None of the above (C) Null

94.

If A2 =A then matrix A is called (A) (C)

Null matrix Identity Matrix

Transpose Matrix (D) Idempotent Matrix

(B)

95.

Let A be an eigenvalue of matrix A then AT, the transpose of A, has an eigenvalue as (A) liA (B) A (C) l+A (D) 1-A

96.

The system of equations is said to be inconsistent if it has (A) (B) (C)

(D)

Unique solution Infinitely small solutions No solution Identity solution

=

97.

The integrating factor of the differential equation x (1+y2) dy + y (1+x2) dx 0 is (A) 1/x (B) lly (C) xy (D) 1/xy

98.

The functions x, x2, x3 defined on an interval!, are always

(C)

Linearly dependent Homogeneous Identically zero or one

(D)

Linearly independent

(A) (B)

99.

The vector field function I is called solenoidal if (A) (C)

curl I = 0 grad i = 0

div I =0 (D) grad div I = 0

(B)

100. In solving any problem, odds against A are 4 to 3 and odds in favour of B in solving the same problem are 7 to 5. The probabibty that the problem will be solved is (A) 5/21 (B) 15/21 (C) 16/21 (D) 69/84

304

14

/ Number :

I

.___ _ ___J

Sign<Jture of the Invigilator (with do.te)

'

COURSE CODE : 304 Time : 2 Hours

Max : 400 Marks

Instructions to Candidates : 1.

2. 3.

4.

\

5. 6. 7.

8. 9.

Write your Number within the box · · ..nd fill in the page 1 of the answer sheet using pe~~oVJded on the top of •' . . h L this _c sheet. V1olat10n of Do not write your na e . . . m anyw er~ booklet "r this enta1ls d1squalifi.cation. / Read each question ca ,1the relevant answer (A) or (B) or (C) or (D) in the relevant bo~e AN'SWER SHEET using HB pencil. Avoid blind guessin~ wrong answer will fetch you -1 mark and the correct

·~f,.l~

-~"

answer will fetch .y{arks. Do not write hing in the question paper. Use the white sheets attached at the works. en the question paper until the start signal is given.

Do -not attempt to answer after stop signal is given. Any such attempt will disqualify your candidature. On stop signal, keep the question paper and the answer sheet on your table and wait for the invigilator to collect them. Use of Calculators, Tables, etc. are prohibited.

1.

The eigen values of the matrix A= [~~ -stn8Jare cos8 (A)

2.

e±19

(B)

(C) ,.:a.e

e±211l

Which one of the following matrices is skew-hermitian? (A)

[~ ~]

(C)

[~ ~]

(D)

[~ ~J

00

3.

4.

The sequence ( ; )

is

(A)

Divergent

(B)

Convergent

(C)

Monotonic increasing

(D)

Oscillating

We have m equations in n unknown and then the coefficient matrix A will be of the type m % n. Let r be the rank of matrix. If r < n, then equation AX = 0 will have (A)

n-r linearly independent solupon

(B)

m-r linearly independent solution

(C)

No linearly independent solution

(D) Infinite number of solutions --"-.. rier cosine transform of f(x) = e-""', m > 0 is (A)

6. (A) (C)

7.

mZ+a

Lic~~.b.o·undru•value problem are known as Root mean square values (B) L...st square values Characteristic values (D) N one "'the above

,Crt(x} + SM(x)]' dx

is equal to

(B)

J:[!(x)]1 [SM(x)Jt

(D)

None Of the above

The solution of xdy - ydx- (1 - x 1) dx = 0 is (A) (C)

304

(C)

mlt+az

£'rt(x)J2 dx + t:=l(a,.- C,.)2 + 1:!':1(C11)r: (A)

8.

m

1

(B)

;+;+x=C ,.

(B)

" 1 -+-+x=C :f

1

---+x=C

(D)

" "

1 -+--x =C

" 2

"

:r

"

9.

10.

11.

12.

13.

· of~'d:y+l . .1s The sou It1on -or-~ = cosx -suu: y" c:.b (A)

y = stnx + Ce"

(B)

y =stnx- Ce"

(C)

,! = sinx + Ce"

(D)

- = -smx + Ce'' 1

3'

If the population of a country doubles in 50 years, in how many years will it be treble under the assumption that the rate of increase is proportional to the number of inhabitants (A)

97 years

(B)

79 years

(C)

75 years

(D)

None of the above

•

The time required for a cylindrical tank of radius 2.5 m and height 3 m to empty through a round hole of radius 25 mm in the bottom of the tank, given that water will issue from such a hole with velocity approximately 2.5../h m/s 'h' being the depth of the water (A)

3 hr 43 min

(B)

3 hr 36 min

(C)

3 hr 34 min

(D)

3 hr 30 min

The differential equation of they =In sln(x- CJ +Cl primitive is (A)

y" - y•z + 1 = 0

(B)

y" + y ' Z - 1

(C)

y" - y' 2 - 1 = 0

(D)

y" + y 12 + 1 = 0

=0

Let 0(:r, y, :r)and 0(:r + Ax,y +Ay, z + Az) be the temperatures at two neighbouring points P(x,y,x)and Q(x + Ax,y +Ay,:z + llz) then (A)

(C)

dC

4'

=V0.~• 41

=V0+

41

(B)

..

~=V0 41

dr b

X 4~

'*•

(D)

None of the above

If n is a constant, then V2 r" is equal to the (A)

n(n-1) ,.n+~

(B)

n(n-1)1"'-~

(C)

n(n + 1) r"+2

(D)

None of the above

The total work done in moving a particle in a force field given F = 3xl - 5xj + 10xk along the curve X = t 2 + 1, y = 2t2 and Z = r& from t = 1 to t = 2 is (A)

313

(B)

(C) 323

333

3

(D)

303

304

3x30-i19

16.

The value of (A)

(C)

17.

18.

20.

21.

22.

304

is

2i-1

+t (1 + t)(l + l)

1

(B)

1-t

(D)

None of the above

A state-variable filter consists of (A)

One op-amp with multiple- paths

(B)

A summing amplifier and two integrators

(C)

A summing amplifier and two differentiators

(D)

Three Butterworth stages

The cos4 9 is equal to 1

1

3

a

a

a

(A)

-cos49- -cos29+-

(B) !.cos46-!.cos29-! a 2 s

(C)

.:.cos46 +.:.cos 29 +!

(D)

None of the above

(A)

-7

(C)

7 +i

8

2

8

(B)

7

(D)

7- i

If A= {1,i,-t},B = {2,1,-t}, C>= {i, - i, 1 +i}&D ={0,-£,1}. Then (AUC)o(BUD)is (A)

{1, i}

(B)

{t, 1}

(C)

{1, -i}

(D)

None of the above

ltm

The ,. --.1+1 (z 2 - Sx + 10) is equal to (A)

5-3!

(B)

5+3!

(C)

(3 + 5t)

(D)

None of the above

When a low- and high- fllter are cascaded to get a band- filter, the critical frequency of the low- fllter must be (A)

Equal to the critical frequency of the high- filter

(B)

Less than the critical frequency of the high- fllter

(C)

Greater than the critical frequency of the high- fllter

(D)

None of the above 4

23.

HW (A)

(C)

ctw

1-z then u

z

.z-1

(i+.z)l

(B)

(Hz)2

z (l-z) 2

(D)

None of the above

ln (z-

feU.18 equal to

24.

25.

=1+z -

v z2±a2

(A)

ln (z ±..Jz2 + a 2)

(B)

(C)

ln (z ± .../z2 + a 2)

(D)

../z2 ± a2 ) In (z + ../zl ± az)

H for a real, continuous function f(x),f(a)f(b) < 0. Then (a.bJ,f(x) = 0 has

m

the range

(A)

Only one root

(B)

At least one root

(C)

No roots

(D)

Indeterminable number of roots

26. The value of (a ±Jbr1 (

A)

o

..•-!?

=!=

.. ± J~ ~

(B)~

J ... b_..

(D)

27.

28.

The power factor of the more reactive load is (A)

Low

(B)

Infinite

(C)

High

(D)

None of the above

What is the average value of the full wave rectified voltage peak value is 15 V? (A)

29.

9.52 V

(B)

9.53 v

(C)

9.55V

(D)

9.54 v

The Clapp oscillator 18 a variation o f - - - - oscillator with a capacitor added in series with the - - - (A)

Hartley, inductor

(B)

Colpitts, inductor

(C)

Wein·bridge, Inductor

(D)

None of the above

304

30.

31.

The magnetic hystersis loop of a material most suitable for use in magnetic storage hard disk is a (A)

Loop with low coercivity

(B)

Loop with high permeability and high saturation

(C)

Loop with low remanence and high saturation

(D)

Square loop.

When Q is Jess than 10, the Colpitts oscillator resonant frequency is (A)

(C) 32.

33.

35.

(B)

tn.J~er

~~ Q -1

Za~!LCr

(D)

2

JLOr 1

lf<_Jl.C;

'\i Q' H

/

"\1 Q"H

(A)

The IF changes by an amount equal to the local oscillator frequency

(B)

The IF stays the same

(C)

The local oscillator frequency changes by an amount equal to the audio frequency

(D)

Both the local oscillator and the IF frequencies change

The operator which represents the two variables should commute if the Poissson bracket of two variables have value 1

(B)

(C)

0

ih

A PLL is locked onto an incoming signal with a frequency of 1 MHz at a phase angle of so•. The VCO signal is at a phase angle of 200. The peak amplitude of the incoming signal is 0.5 V and that of the VCO output signal is 0.5V and that of the VCO output signal. The VCO frequency and the value of the control voltage being fed back to the VCO at this point are (A)

2 MHz, 0.152 V

(B)

1 MHz, 0.3 V

(C)

1 MHz, 0.152 V

(D)

None of the above

An external transistor is used for (A)

Increasing the output voltage

(B)

Improving the regulation

(C)

Increasing the current that the regulator can handle

(D) Short-circuit protection

304

lg

21r

When a receiver is tuned from one RF frequency to another

(A)

34.

1

6

--

.........

36.

37.

38.

39.

40.

41.

The characteristic that allows an isolation amplifier to amplify small signal voltages in the presence of much greater noise voltage is its (A)

CMRR

(B)

High gain

(C)

High input impedance

(D)

Magnetic coupling between input and output

When negative is used, the gain bandwidth product of an op-amp (A)

Increases

(B)

Decreases

(C)

Remains same

(D)

None of the above

The SCS differ from the SCR because (A)

It does not have a gate terminal

(B)

Its holding cu.r rent is less

(C)

It can handle much higher currents

(D)

It has two gate terminals

The PUT is (A)

Much like the UJT

(B)

Not a thryristor

(C)

Triggered on and off by the gate-to-anode voltage

(D)

Not a four-layer device

A thyristor has (A)

Two pn junctions

(B)

Three pn junctions

(C)

Four pn junctions

(D)

Only two terminals

An amplifier has the following critical frequencies 1.2 kHz, 950 Hz, 8 kHz & 8.5 kHz.

The bandwidth is (A)

42.

43.

7650Hz

(B)

7300Hz

(C)

6800Hz

(D)

7060Hz

In the step response of a noninverting amplifier, a longer rise time means (A)

A narrower bandwidth

(B)

A lower critical frequency

(C)

A higher upper critical frequency

(D)

None of the above

The gain of a certain amplifier frequency decreases by 6 dB when the frequency is reduced from 1 kHz to 10 Hz. The roll-off is (A) -3 dB/decade

(B)

-6 dB/decade

-3 dB/octave

(D)

-6 dB/octave

(C)

7

304

44.

45.

46.

The midrange voltage gain of a certain amplifier is 100. The input RC circuit has a lower critical frequency of 1 kHz. The actual voltage gain at f = 1 kHz, f = 100 Hz and f= 10Hz (A)

70.7, 10, 1

(B)

7.07, 10, 1

(C)

7.07, 50, 25

(D)

None of the above

Cross over distortion is a problem for (A)

Class A amplifiers

(B)

Class AB amplifiers

(C)

Class B amplifiers

(D)

All of these amplifiers

In a certain common-source amplifer, R0 = 1 k!l, Rs = 560 !l, V00 = 10V and gm = 4500 pS. If the source resistor is completely byed the volt~ge g,ain is (A)

47.

450

(B)

45

(C)

4.5

(D)

2.52

Ideally, the equivalent circuit of a FET contains (A)

A current source in series with a resistance

(B)

A resistance between drain and source terminals

(C)

A current source between gate and source terminals

(D) A current source between drain and source terminals 48. A TMOSFET is a special type of

49.

(A)

D·MOSFET

(B)

JFET

(C)

E-MOSFET

(D)

Answers (A) and (C)

The decimal number 175 is equal to the binary number (A)

50.

11001111

(B)

10101110

(C)

11101111

=

AB fAC + ASc is equal to (A)

304

(D)

A pulse is applied to each input of a 2-input NAND gate. One pulse goes HIGH at t =0 and goes back low at t = 1 ms. The other pulse goes HIGH at t =0.8 ms and goes back low at t = 3 ms. The output pulse can be described as follows (A) It goes LOW at t = 0 and back HIGH at t = 3 ms. (B) It goes LOW at t =0.8 ms and back HIGH at t =3 ms. (C) It goes LOW at t 0.8 ms and back HIGH at t 1 ms. (D) None of the above

=

51.

10101111

A +m:'

(B)

A1J + C

(C)

8

A +Bl'

(D)

A +lrF'l'

52.

53.

64.

'

On a Karnaugh map, grouping the Os produces (A)

A product-of- sums expressions

(B)

A sum-of-products expression

(C)

A "don't-care" condition

(D)

AND-OR logic

The output expression for an AND-OR-Invert circuit having one AND gate with inputs A, B, C and D and one AND gate with inputs E and F is (A)

ABCD+EF

(B)

(C)

(A + B + C + D)(E + F)

(D)

A BCD-to-7 segment decoder has 0100 on its inputs. The active outputs are (A)

55.

56.

57.

58.

a, c, f, g

(B)

b, c, f, g

(C)

b, c, e, f

(D)

b, d, e, g

In general, a multiplexer has (A)

One data input, several data outputs and selection inputs

(B)

One data input, one data output, and one selection input

(C)

Several data inputs, several data outputs and selection inputs

(D)

Several data inputs, one data output and selection inputs

The purpose of the clock input to a flip-flop is to (A)

Clear the device

(B)

Set the device

(C)

Always cause the output to change states

(D)

Cause the output to assume a state dependent on the controlling (S-R, J-K or D) inputs

Which one of the following is an example of a counter with a truncated modulus? (A)

Modulus 8

(B)

Modulus 14

(C)

Modulus 16

(D)

Modulus 32

A 10 MHz clock frequency is applied to a cascaded counter consisting of a modulus-5 counter, a modulus-8 counter and two modulus-10 counters. The lowest output frequency possible is (A)

59.

A+B+C+!J+E+F (A t B + C + l5)(E +F)

10kHz

(B)

2.5 kHz

(C)

5kHz

(D)

25kHz

A modulus-10 Johnson counter requires (A)

Ten flip-flops

(B)

Four flip-flops

(C)

Five flip-flops

(D)

Twelve flip-flops

9

304

60.

With a 100kHz clock frequency, eight bits can be serially entered into a shift (A)

61.

62.

63.

64.

65.

66.

67.

304

80 j.IS

(B)

8 \lS

(C)

80

0\S

(D)

10 }lS

Optical storage device employs (A)

Ultraviolet light

(B)

Electromagnetic field

(C)

Optical couplers

(D)

Lasers

AROMisa (A)

Nonvolatile memory

(B)

Voltaile memory

(C)

Read/write memory

(D)

Byte-organised memory

The main advantage of ECL over TTL or CMOS is (A)

ECL is less expensive

(B)

ECL consumes less power

(C)

ECL is available in a greater variety of circuit types

(D)

ECL is faster

A positive-going pulse is applied to an inverter. The time interval from the leading edge of the input to the leading edge of the output is 7 ns. This parameter is (A)

Speed-power product

(B)

Propogation delay, tPLH

(C)

Pulse width

(D)

None of the above

OLMC is acronym for (A)

Output Logic Main Cell

(B)

Optimum Logic Multiple Channel

(C)

Output Logic Macrocell

(D)

Odd-parity Logic Master Check

FPGA stands for (A)

Fast propogation gate array

(B)

Field presettable gate application

(C)

Field programmable gate array

(D)

File programmable gate array

A varactor diode exhibits (A)

A variable capacitance that depends on reverse voltage

(B)

A variable resistance that depends on reverse voltage

(C)

A variable capacitance that depends on forward current

(D)

A constant capacitance over a range of reverse voltages

10

68.

69.

70.

The doping of a semiconductor with a p-type dopant creates, in the bandgap, (A)

Filled states near the conduction band

(B)

Empty states near the conduction band

(C)

Filled states near the valence band

(D)

Empty states near the valence band

The condition(s) that indicate that a material is superconducting are (A)

Zero resistance

(B)

:Flux exclusion

(C)

Zero resistance and flux-exclusion

(D)

None of the above

The I and voltage across 7 0 is for the network is +V70

Hl

+

12.5 v

50V

40

71.

(A)

2.5A 17.5 V

(B)

2 A, 17V

(C)

2.5 V 17V

(D)

2A, 17.5 V

The voltage V1, V2 and I for the given network are

72.

The voltages v,, V2 and Vs of the network are

(A)

(C)

12 V, 7 V, 15 V 12V, 7V, 19 V

(B) (D)

12 V, - 7V, 15V None of the above

73.

The impedance of the parallel LCR circuit at resonance is (A) Maximum (B) Minimum (C) Average value (D) None of the above

74.

The current through the 70 of the network is 60 1

It t

.

•

,.. .•

80

~

~:..

.1

n

.; 9V

75.

(A)

0.097 A

(C)

-{).971 A

(B) (D)

A network configuration typically having a diamond appearance in which no two elements are in series or parallel is known as (A) Wye network (B) (C) Bridge network (D)

76.

304

0.971 A None of the above

Ampere's circuit None of the above

The current I in any branch of a network, due to a single voltage source E anywhere else in the network, will equal the current through the branch in which the source was originally located if the source is placed in the branch in which the current I was originally measured (A) Superposition theorem (B) Substitution theorem (C) Milliman's theorem (D) Reciprocity theorem

12

77.

78.

79.

80.

Shot noise arises in the semiconductor devices due to the (A)

The random diffusion of minority carriers

(B)

The random generation and recombination of hole·electron pairs

(C)

Answers (A) and (B)

(D)

None of the above

The advantage of using a junction diode as temperature stabilizing element in transistor amplifier is (A)

Its temperature coefficient of resistance is negative

(B)

It is made of the same material as the transistor

(C)

Its reverse current is low

(D)

Its resistance changes with change in temperature

Which of the following is not a characteristic of UJT? (A)

Intrinsic standoff ratio

(B)

Negative resistance

(C)

Peak-point voltage

(D)

Bilateral conduction

(B)

Will raise the resistance of the coil

A ferromagnetic core if placed inside a coil (A)

Will decrease the coil inductance

(C) Will lower the resistance of the coil 81.

82.

83.

(D) Will increase the coil inductance

A better power supply should possess (A)

Higher input impedance

(B)

Lower output impedance

(C)

Lower input impedance

(D) Total voltage regulation

A radio wave has a maximum electric field intensity lQ-4 Vm-1 on arrival at a receiving antenna. The maximum flux density of such a wave is (A)

Zero

(B)

(C)

5.8 X 10-9 T

(D)

3 X 104 T 3.3 X lQ-13 T

In the case of reflection and refraction of light at the dielectric interface

(A) Tangetial components of D and

B are continuous

(B)

Tangetial components of D and normal component of B are continuous

(C)

Normal components of D and B are continuous

(D)

Normal components of D and tangential components of B are continuous

13

304

84.

85.

86.

The Poynting theorem is a mathematical statement of the conservation of (A)

Momentum

(B)

Charge

(C)

Electromagnetic theory

(D)

States

The electromagnetic theory suggests that the electric vector in the wave suffers a sudden phase change of It on reflection from the plane reflecting surface but the magnetic vector suffers (A)

A phase change of n

(B)

A phase change of 2n

(C)

A phase change of 1fl2

(D)

No phase change

An infinitely long hollow cylinder of radius R carryinr: a surface charge density o is

rotated about its cylindrical axis with a constant angQ.ar speed cu. The magnitude of the surface current is (A)

87.

88.

o&.l

(B)

2o&.l

(C)

1to&.l

(D)

2no&.l

The force which is always directed away or towards a flXed centre and magnitude of which is a function only of the distance from the fixed centre, known as (A)

Coriolis force

(B)

Centripetal force

(C)

Centrifugal force

(D)

Central force

Equation of motion for bead sliding on a uniformly rotating wire in a force free space IS

(C)

89.

(B)

X mQ!B O 11+--= I

(D)

None of the above

A cube has side L. when at rest. H the cube moves with velocity v parallel to its one

edge then its volume becomes

90.

304

(A)

r.,a

(B)

L.s(1- ;z) -11<

(C)

L.a(1- ;.2 )

(D)

r.,a(1 -

7

;', ) \Ia

The unit of Hall coefficient is (A)

V ms A wb-1

(B)

V m A wb-•

(C)

vms A-• wb-t

(D)

Vm2A-2wb

14

91.

If a body is thrown vertically upwards, it strikes the ground at (A)

a ruh cos.., (~"· -;) w" to the west 16

..

(C) ;_tuh cos0(2h) s

92.

l/Z

to the west

11 -

wh cos0(~)

(B)

1 :

(D)

i wh cos0 (~) 112 to the east

liZ

to the east

Alogrithm and flow chart are both (A)

Different procedures

(B)

The same procedures

(C)

Different ways show the same procedure

(D) All three are correct

93.

94.

95.

In algorithm in all steps (A)

Different activities takes place

(B)

Same activity is repeated

(C)

Same activity is shown by different methods

(D)

Activity is started

In 8085, when the operand is specified within the instruction itself, the addressing mode is (A)

Direct addressing

(B)

Indirect addressing

(C)

Indexed addressing

(D)

Immediate addressing

A block with a mass of 200 g is connected to a light spring for which the force constant is 5.00 N/m and is free to oscillate on a horizontal, frictionless surface. The block is displaced 5.00 em from equilibrium and released from rest, as shown in figure. The acceleration of the mass is given by

(A)

a= ( -1.25 m/s2 ) cos(5t)

(B)

a= (1.25m/g2) cos(5t)

(C)

a= (-1.25 m/s2 ) sin(5t)

(D)

a

15

= (0.05 m/s2 ) cos(5t) 304

96.

97.

98.

A transverse wave is represented by the equation y=yo sin[(2WJ..)(vt-x)). For what value of A is the particle velocity equal to two times the wave velocity? (A)

A = 2cyo

(B)

A = eyo/3

(C)

A= cyo/2

(D)

A= 1tyo

A massless spring of force constant k has masses mt and lll2 attached to its two ends. The system rests on a horizontal table. The angular vibrational frequency c.> of this system is (A)

[

(C)

[

Jt/Z

(B)

ir{m;,+m,}] 1/2

[

,

..,., I<

]

u;~

(D)

"'-!~

An open vessel containing water is given a constant acceleration a in the horizontal direction, then the free surface of water gets sloped with the horizontal at an angle 6 given by (A) (C)

99.

I<

.....-.....

a=tan-•(alg) a=sin-1(a/g)

(B) (D)

a= tan-•(g!a) a = cos-•(alg)

An uniform line charge distribution with linear charge density of 3.30 nano Coulombs per meter is located at x = 3 meters and y = 4 meters. The electric field strength at origin is thus :

(A) -7.13 i-9.50jV/m

(B)

7.13 I- 9.50 j V/m

(C)

(D)

-7.13 I+ 9.50 j V/m

7.13 I+ 9.50 j V/m

100. Which of the following statements is false about the differences between 8086 and 8085 microprocessors? (A)

Each instruction is fetched, decoded and executed before processing of next instruction in 8085; whereas, in 8086, while one instruction is executed, the fetching and deoding of succeeding instructions concurrently takes place

(B)

8086 has 116 bit data bus while 8085 has a 8-bit data bus

(C)

8086 stack pointer is a 20 bit while 8085 stack pointer is a 16-bit

(D) . 8086 has a 20 bit bus for physical addressing while 8085 has a 16 bit address

bus

304

16

ENTRANCE EXAMINATION FOR ISSION, MAY 2011. M.Tech. (ELECTRONICS)

COURSE CODE : 304 Number :

~. .I

_ _ _ __

__J

Signature of the 1nuigi/ator (with date)

COURSE CODE: 304 Time : 2 Hours

Max : 400 Marks

Instructions t:o Candidates : 1. 2.

Write your Number within the box provided on the top of this page and fill in the page 1 of the answer sheet using pen. Do not. write your name anywhere in this booklet or answer sh eet. Violation of this entails disqua lification .

3.

Read each quest ion carefully and shade the relevant answer (A} or (B) or (Cl or (D) in t he relevant box of the ANSWER SHEET using HB pencil.

4.

Av01d blind guessing. A wrong answer will fetch you - 1 mark and the correct answer will fetch 4 marks.

5.

Do not write anything in the question paper. Use the white sheets attached at the end for rough works.

6.

Do not open the question paper until the start signal is given.

7.

Do not attempt to answer after stop signal is given. Any such attempt will disqualify your candidature.

8.

On stop signal, keep the quest ion paper and the answer sheet on your table and wait for the irwigilator to collect them.

9.

Use nf Calculators, Tables, etc. are prohibited.

1.

2.

3

Each of three coins has two sides, heads and truls. Represent Ihe hl•ads m· tails statu.<; of each coin by a logJcal variable \A for the flrsl c<>in. B for the ~ccond colD and C for the third) whore the logical Yanal>le IS J for heads and 0 lor l.;d~. '('hen a logtc function F (A,B,C) wruch 1s I iff exactly one of t.hc coins is head~ after a toss of U1c coins can be wriUt•n in tet·ms of a rum term llxpans10n lA)

L:m(l,2,4)

(B)

!C)

fl m(l,2,4)

10)

L M (1,2,4) IT M(I,2.4) !C + 0)
BCD + C'D' - B'C'D' • CD JS equal to !AI

lC' + Dl + (C' + o· + BJ

!B)

(CJ

(C' +D) (C + D' + B'l

IDJ None of the above

The company safe should be ur.Uocked (U) only when Mr. Jonu~ (J 1 HI in the office or Mr. Evans tEJ IS in ~he office, and nnly when the company is open for bUSlDess (B), and only when the .;ecunty guard (S) 1s present This can be represented by a Boolerui ~uation

= tJ.Elt.B + R)

tAl

U

lC l

U = (J' ; E) BS

If the function f1 (a,b,c) mo + 11L2 + of products can bo written as

nl&

03)

U = (J ~ E)!B + SJ

( DJ

U =(,J + E) BS

+mu. Us1ng a Kamaugb mup the mininlum

«11111

tAl t CJ

1;,

f= b'c+a'c' + ab'c f = be' + a'c' + nbc'

(8)

I = be'+ a't•' + ab'c

10)

f= be'+ a'c + nb'c

'l'he circuit below was deStgned to tmp1emont Lite logic equation J? .,. AB'D + BC'D' + BCD, buL it i:> not worlcing properly. 'L'ht• input wires to gates 1,2 and 3 nr" so tightly pncked, it would Luke you a wrule to tr·nce them all back Lo sec whet.her mputs are co.n-eci. It would be nice io only have to trace whichever one tS incorrectly wired. When A= B = 0 and C "' 0 = 1. the inputs and outputs of gate 4 are as shown. Then, which of the gales r1ther is connected mcorrect ly Ol' is malfunctiorung

M£~5

,

c -

w~~s

[0-

I

-B-- -:8

f

D

tA)

304

Gate I

tBt

Gate2

l('l

2

Gate 3

(lll

Gatto -1

n.

Flip-flop shown in figure behaves as

~~--:-.l:~ 7.

f.Al

Reset dominant flip llop

(B)

RS flip flop

(C)

Set dominant flip flop

(D)

Master-slave flip flop

A latch can constructed from an OR gate, an AND gate and an inverter connected as follows. V.lhat restriction must be placed on R and H so that P will always equal Q' under steady state conditions?

R

p H

1>.

9.

10.

=0 cannot occur a t the same Lime

(A)

R:: l and R

(B)

R = 1 and H = 1 cannot occur at the same time

(C)

R = 0 and H

(0 )

None ofthe above

=0 cannot occur at the same time

A 'C + B 'C' + AB is equal l o (A)

tA + B)'C

(B}

AB + B'C' + AC'

(C)

<\'B' + BC + A'C

!D)

A'B' + BC + AC'

Binary equivalent. of 0.625,o (AJ

.101

(B)

.110

(())

011

(D)

None of the above

How many switching functions of two variables lx andy ) arc Lhere? IAl

8

(Cl

24

3

16

(Dl

32

304

11.

12.

13.

14.

The Laplace transform of {t 2 -2t )u (t - 1) is tAl

2/s 3 e·•- 2/s 2 e·'

(C)

2/s 3 e-• -1/s 2 e-•

tA)

){e'u(-t)+l/2e'u(t)

CB)

Xe'tl/2(e·'-e')u(t)

(CJ

,Xe-1 u(-t)+l/2e-1 u(t)

(D )

Xe'u(-t)-1/2e-•u(t)

The energy of a signal n u [t] is (A)

n

(n + 1)/2

(B)

n(n Tl) (2n + 1)/6

CC)

(n (n + l)/2)a

""

(C)

4s

(D )

'II s

(C)

rh.-a T

(0)

zlz+a-T

17.

8s

zlz-aT

(B )

= a•T is

zlztar

tAl

HighQ

(B)

Low Q

(C)

Low resonant frequency

(0 )

High resonant frequency

The copper armature winding of a motor is s ubjected to an operating temperatw·e of 80° C. The room temperature is 20" C. The percentage change in resisLance of t.he aTtnature winding from cold starting condition to normal running will be nearly 10%

(B)

(C)

16%

20%

(D)

24%

The current through an electrical conductor is 1 ampere when the temperature of the conductor is 0 o C and 0.7 ampere when the temperature is 100 o C. The current when the temperature of the conductor is 1200 a C must be

0.08 A

(B)

(.C)

0.16A

0.32 A

( D)

0.64 A

Two coils irt different connection have self inductance of 2 mH and 4 mH and amutual tnductance of 0.15 mH. The equivalent inductance of the combinat10n is (A)

304

(BJ

is

A coil with large distributed capacitance has a

lA) 19.

1/8 s

The Z-transform F(z) of f(nT)

18.

JT /4(t-1)

The period of the function cos

(A)

16.

None of the above

The auto-correlation of the signal x (t) = e -• u (t) is

tAl 15

(D)

5.7mH

(B)

{C)

5.85mH

4

GmH

6.15mlf

20.

At a certain current, the energy stored in !ron cored coil is 1OOOJ and its coppet·loss is 2000w. The time constant (in seconds) of the coil is (A)

21.

0.25

lBl

(Al

24,

27

(B)

2~ 15

(A )

50 Q

\C)

7.69+jl1.54

f. What is the effective area of the antenna?

75m2

(C)

50 m 7

(D)

25m 2

(Bl

~/5

CDl

20_..1

Q

(B)

100+j150 Q

(D )

7.69-jll.54

Q

When a plane wave travelling in free-space is incident normally on a medium having £, = 4 , then fraction of power transmitted into the medium is given by 8/9

(B)

1/2

(C)

1/3

(D)

5/6

A rectangular waveguide having TElO mode as dominant mode is having a cut-of! frequency of 18 GHz for the TE30 mode. The inner broad-wall dimension of the rectangular waveguide is (A)

26

100m2

meters can be

Characteristic impedance of a transmission line is 1)0 Q. Input impedance oftbe open circuited line is Zoe = 100 + jl50 Q When the transmission line is short-circuited, then value of the input impedance will be

(AJ 25

= 10

2

A most antenna consisting of a 50 meter long vertical conductor operates over a perfectly con ducting gr ound plane. It's base -fed at a frequency of GOO KHz. The radiat.i on resistance of the antenna in ohms is lA)

2a.

(D )

The actual gain of a p1uabolic antenna of diameter D approximated by G = 2n (D I),

22.

1

0.5

5/3 em

(B)

(C)

5 em

5/2 em

(D)

10 em

In a two-element senes vtrcuit, the applied voltage and the resulting cun-ent are r espectively v(t) = 50 + 50 sin(5 X103 t)v and iltl = 11.2 sm(5 X 103 t + G3A 0 lA. The nature of the element would be

(A) L-L

(B)

R-C

(Cl

(D)

Neither R nor L nor C

L-C

Give lwo coupled rnductors Ll and L2, their mutu.tl inductance M sallsfies IR)

M > (Ll+£2) 2 5

(C)

(0)

Ms~L 1 L~ 304

28.

A voltage waveform v(t) = 12t 2 is applied across a lH inductor for t Z 0, with initial ~:urrent through it being zero. The current t.hrough the inductor for t 2: 0. is given by (Al

29.

51.92 KHz

=1 p F. The lower half power

3.055 KFlz

CD)

L92 KHz

V/2R

(B)

V/3R

(C)

v/J2R

(D)

../2V/R

2{3Q

(Bl

(C)

lQ

3Q

(D)

1/3 Q

R

(B)

c

(C)

L

(D l

All of these

(B)

2

0.5

(C)

4/3

0.2 v

(C)

2v

10 v

50 v

Z-parameter

(B)

h-parameter

(CJ y-parameter

{D)

ABCD-parameter

(C\

~~ ln(9)

9

Evaluate

J..fr ln(x)dx I

(A) 304

If

'l'wo 2-potrt networks are c01mected in cascade. The combination is to be represented as a single two-port network. The parameters of the network .are obtained by multiplying the inilividual

(Al

36.

= lH.

A ramp voltage v{t) = 100 volts, is applied to an RC differentiating circUtt. with R = 5 K Q and C =4 Jl F . The maximum output voltage is

35.

L ~ 100 p F and C

The thevenin resistance of the network comprising of a resistor of 1 Q in series with a parallel co=unication of a current source of 21 amperes and a resistor of 1 Q through which 1 ampere of current flow is

<M ;34

(B)

Q,

12 tJ

The value of current at resonance in a series RLC circuits is affected by the value of CA)

33.

30.55 KHz

(C)

A voltage u (t)=6e-21 is applied at t =0 to selies R-L circuit with L i (t)=6 [exp (- 2t)- exp- (- 3t))then R will have a value of

32.

24 t

The power in a seties R-L-C circuit will be half of that at resonance wl1en the magnitude of the current is equal W (A)

31.

(B)

A series R·L·C circuit has R =50 frequency of the circuit i.s (A)

30.

12 t

28

(Bl

0.444 6

(D)

25.5

37.

Calculate tl1e linear correlation cocfficumt for the data points 10

20

30

50

40

0.22 0.40 061 0.85 1.20

lA)

0.99633

(Bl

0 91919

(C)

60

I

70

1.4511 70

0.99268

COl

0.82900

._, tl f . f( ) { 1 when x ts irrational.. Con.' rel="nofollow">1uer · 1e unchon x = -1 when x is ration11L

39

(A)

The lunclion is differenttablo everywhere

(8)

The function is contiouoos everywhere

I C)

The function is discontinuous at all rational points

(0)

The funcl.ion is contmuous but not differentiable at rational po•ot:;

CollSlder a right angled lnanglc whose hypotenuse is hand bas<' of x, the area of the tnangle Will be a max.imwn? (D)

10.

JJ.

x

IS

x. For whal value

h/J2

Wluch one of the following stalement.s \s true? (A)

The eigenvalues of skew-hernuban mat.rix ten not be zero

(8)

A 3)1ll.lllCtric square

tCI

The eigenvectors correspond.tng to are not hnearly independent

(I))

The eigenvalues uf Hcrmtlian matnx are real.

The differeoilal equat•on

matrlX cannot be always dJagooaliY..able.

I:~

I·IYI

+c-= O,c> 0

(A)

Has no solution

(B)

lias unly one trivinl solution

\CJ

Does not have a unique solution

(D)

Has a umque solution

lA)

cot"1 (s/w)

(C)

cot-' (w/s)

7

IDl

lan

1

(W/s)

304

43.

Let the complex number

-r w Then, the Cauchy·R•emann equations in polar

"='II

coordinates are !A)

ou "'~" ou. or

a'n d Ciu =_lou aB r or

il B '

au 1 ilu -:o---

ar

44.

45.

au

(D)

and - " ' r r CIB ' B

The residue at (A)

i)u

( B)

a

or

au

lou

au

au

- = - - - and - = r oO rar' ilr iJB

z"'~ of the complex function f(z)=z~ cos(~ ) is

Zero

(B)

(C)

One

Infinity

(D)

-1

The Wronsltian of the functions e• ,e:u ,ea- is equal to (B)

6 e2.x

16.

A 90kHz bandwidth is to accommodate 6 Am broadcasts simultaneously. What ma,ximum modulating frequency must each station be limited to? (D) 3500Hz (Cl 7500Hz (B) 5500 H;~. (A) 1500Hz

47

What function is served by the limiter in an FM receiver? (Bl to remove frequency variation (A) to remove the noise variation (C)

48.

49.

(A)

increases

{B)

decreases

(C)

may increase or decrease

(D)

remains unaffected.

Which of the following represents the noise figure?

304

!Dl

(C)

(B)

The order of error in the Simpson's rule for numerical integration with a step size is (A)

51.

to remove interference signal

Due to refraction of TV signal in troposphere, the range

CA) 50.

(D)

to remove amplitude variation

h

(Bl

h2

(C>

h3

(D)

Phase margin of a system is used to specify

frequency response

(B)

t•me response

(C)

telative stability

(Dl

absolute stability

8

h'

52.

53.

54.

55.

A system has poles at -1 and -5 and zeros at 1 and -2 the system is (A)

marginally stable

(B)

(C)

unstable

CD J stable

The Bode plot of the transfer function G(s)=s (Al

constant magnitude and constant phase shift angle

(BJ

-20 dB/decade and constant phase shift angle

(C)

20 dB/decade and phase shift of ;r /2

(D)

zero magnitude and phase shift

An instruction used to lhe carry flag in a computer can be classified as (A)

data transfer

(B)

arithmetic

tCJ

logical

(D )

program control

The nu.m ber of memory cycles required to execute the 8085 instruction LDA 3000H would be

(AJ l'i6.

4

(8)

2

(C)

3

(D)

5

(D)

12 btts

The length of Program Counter of8085 microprocessor is (A)

57.

highly stable

16 bits

{Bl

6 bits

(C)

8 bits

The following program starts at location OlOOH. LXI SP, OOFF LXJ H, 0701 MVT A, 20H

SUBM The content of accumulator when the progra111 counter reaches 0109H is

58.

.20H

(Bl

.02H

(C)

.OOH

(D)

FFH

Modem computer possess

decimalmlmbers

(8)

hexadecimal numbers

!C)

digits and strings

(D)

binat·y numbers

9

304

59.

flowchart ts a diagrammatic repre;;entation

mrucatmg the events occurrang in the logtcal sequence and showmg the tnter· relation between them

60

61

ti2.

63.

(l.j

115

304

(B l

indicating the events of pbystcal system

(())

of a chart indicating the flow of process

t U)

a ny of the above

vVho

i~

U\)

Pascal

(B)

Charles Babbage

tCl

John Napier

IDI

Abacus

regarded as a father ol computer?

F'lug bits in anthmettc unit provide whtch oft he f<)llawing? IM

l<~acilities

1Cl

Sta~us

(B)

for re-check

Repeatability

(D) All of the above.

type information

The limitation of e-beam lithography tS

Jess resolution

(B)

less throughput

(0)

le:;s current densi l1es

I D)

none of the above

The dosadvantage of Lon lmplant
hogh vacrum conclitions

tB)

htgb tempemlure

1r1

expensive

tD)

none of the above

NMOS is prefened than PMOS

IAI

high switch ing speed

l.Bl

J<:ss power russipal.ion

tCl

high package denst ty

10)

all the above

The open loop Lransfer function of a control system ts G!sl lA I

lypl.' zero system

!Bl

type-1 system

((')

type-2 system

10 l

type-3 svstem

10

1\1 < I It•)

66.

A diode circuit with an LC load is shown in Figure with Lhe capacitor having an initial voltage of Vo = 220V, Capacitance = 20 p F and inductance L 80 pH. lf switch is closed at l = 0, then the peak cu••ent through the diode and the conducting lime of a eli ode is

=

L

0

67.

68.

(Al

110 A, 125.66 s

!B)

llOA, 125.66 ms

tCl

110 A, 125.66 minutes

(D)

100 A, 125.66 p s

The lowering of the energy barrier al the r.athode because of the positive gradic.:nt of pulential at cathode is commonly known as tA 1

Skin effect

IBl

Johnson effect

tC l

Avalancb mechanism

\D)

Schotkky e!Iect

An operational amplifer having a slew rate of 2 V/ iJ s . The maximum closed loQp voltage gain that can be used when the input single vanes by 0.5 V in 10 p sus

('\) 69.

20

\Bl

tC)

30

40

(D)

50

An LC filt.er shown in figure is used to reduce the ripple constant of the output voltage for il single phase full wave rectifier. The nth harmonic ripple current to through the filter capacitor, the load impedance must be that of the capacitor

+

v

70.

R

Much greater thllll

1BJ

M11ch lower than

tC rel="nofollow">

Equal to

(0)

None oft he above

A capacitive transducer is mad{' up of two capacitive ryllndrical electrodes. The outer diameter of t.he inner cylinder electrode is 3 mm and the dielectric medium is air. The inner djameter of elect.rode is 3.1 mm. The clielectric stress when a voltage of 100 Vis applied across electrode is

2 kV/hour

(B )

2 kV/min

(C) 11

2 kV/sec

tD rel="nofollow">

2 kVIm

301

71.

72.

73.

74.

For a practical amplifier, the overall gain is greater if the internal resistance of the signal source is (A)

Small

(B)

High

(C)

Infinite

(D)

None of the above

The circuit is used to decrease gain and increases both the input and output impedance of the amplifier (A)

Voltage series

(B)

Current series

(C)

Voltage shunt

(D)

Current shunt

A bipolar junction transistor has beta ( jJ) value of 62, then alpha (a) is given by (A)

0.0984

(B)

9.84

(C)

0 984

(D)

Data is not enough

The frequency of oscillation of three stage ladder network oscillator in which C = 10 nF & R= 10 k Q is (A)

75.

77.

304

(B)

647khz

(C)

674Hz

(D)

647Hz

The amplifer utiliz.es n-channel FET for which Vp = -2.0V, g.,. = 1.6 rnA/V & loss =1.65 rnA. It is designed to bias the circuit at Io = 0.8 rnA using Voo = 24 V. Assume rc1 >> Rl, then Vcs is equal to (A)

76.

674kHz

-0.62 V

(B)

0.62 V

(C)

-6.2 V

(D)

6.2V

Hysteresis is desirable in Schmitt-trigger, because (A)

energy is to be stored/discharged in parasitic capacitances

(B)

effects of temperature would be compensated

(C)

devices in the circuit should be allowed time for saturation and desaturation

(D)

it would prevent noise from causing false triggering

The control terminal (pin5) of 555 timer IC is normally connected to ground through a capacitor (- 0.01 f.J F). This is to (A)

protect the IC from inadvertent application of high voltage

(B)

prevent false triggering by noise coupled onto the pin

(C)

convert the ttigger input to sharp pulse by differentiation

(D)

suppress any negative triggering pulse 12

78.

79.

80.

The reverse- saturation current of a silicon diode (A)

doubles for every 1o•c increase in temperature

( B)

does not change with temperature

(C)

halves for every 1•c decrease in temperature

(D)

increases by 1.5 times for every 2•c increment in temperature

Wien bridge oscillator can typically generate frequencies in the range of (A)

1 KHz - 1 MHz

(B)

1 MHz- 10 MHz

(C)

10 MHz - 100 MHz

(D)

100 MHz- 150 MHz

In the voltage regulator shown below, if the current through the load decreases, Rl

c fD 81.

82.

83.

(A)

The current through R1 will increase

(B)

The cu rrent through R1 will decrease

(C)

Zener diode current will increase

(D )

Zener diode curren t will decrease

The main advantage of a crystal oscillator is that its output is (A)

50Hz to 60Hz

( B)

variable frequency

(C)

d.c

(D)

a constant frequency

Just as a voltage amplifier amplifies signal-voltage, a power amplifier (A)

Merely converts the de power into useful ac power

(B)

Amplifies power

(C)

Amplifies signal current

(D)

Merely converts the signal ac power into the de power

The forward characteristic of a diode has a slope of approximately 50mAN at a desired point. The approximate incremental resistance of the diode is (A)

84.

~''

50

Q

(B)

35 Q

(C)

20

Q

(D)

10

Q

The width of depleted region of a PN junction is of the order of a few tenths of a (A)

Millimeter

(B)

Meter

(C)

13

Nanometer

(D)

Micrometer

304

85.

86.

The important characteristic of emitter-follower is (A)

high input impedance and high ou tput impedance

(B)

high input impedance and low output impedance

(C)

low input impedance and low output impedance

(D)

low input impedance and high output impedance

A straigh t horizontal length of copper wire has a current i"'28 A through it. The mass

per u nit length of copper is 46.6 gm· 1 What is magnitude of the magnetic field B needed to suspend the wire in air (that is to bala nce gravitational force on it)?

87.

(A)

0. 16 T

(B)

28 times the strength of earth's magnetic field

(C)

0.28 T

(D)

1.6 X

lQ-2 T

The moment of inertia I of a solid sphere of mass M a nd radius R about any diameter is

88.

(B)

(A)

(D)

A unifonn solid cylindrical disk of mass M =1.4 kg and radius R=8.5 em rolls smoothly across a horizontal table at a speed of 15 em s- 1• The kinetic energy K of the disk is (Al

89.

K = .01575

(B)

K = 157.5 J

(C)

K = 0.24 J

(D)

The potential energy of a particle in a field is of the form U

K = 0.024J

(r)=(,~ -~)where the

constants are a>O and b> 0 and r is the distance of the particle from the center of the field . The maximum force is

304

3

(A)

d. I . F nt•x = -b32 an IS repu s1ve

(Bl

F.,.. = b

(C)

d. I. Fn>nx =-b22 an IS repu s1ve

(D)

F'""' =~ and is attractive · 27a

27a

27a

14

27a 2

and is attractive

90.

A uniform disk, a thin hoop and a uniform sphere, all with the same mass and same outer radius, are each free to rotate about a fixed axis through its center (see below figure). Assume the hoop is connected to the rotation axis by light spokes. With the objects starting from rest, identical forces are simultaneously applied to the rims, as shown. Rank the objects according to their angular acceleration, least to greatest

91.

(A)

Disk, hoop, sphere

(B)

Hoop, disk, sphere

(C)

Hoop, sphere, disk

(D)

Disk,sphere,hoop

'l'wo ideal monoatomic gases are in thermal equilibrium with each other. Gas A is composed of molecules with mass m while gas B is composed of molecules with mass

4 m. The ratio of the average molecular speeds u.4 fu 8 is (A)

92.

~

Yz

(B)

(Cl

2

(D)

1

The pressure of an ideal gas is doubled in an isothermal process. The root-meansquare speed of the molecules

93.

94.

(A)

Increase by a factor of

(C)

Decrease by a factor of

../2 1 ../2

(B)

Does not change

(D)

Increase by a factor of 2

The Maxwellian speed distribution provides a direct explanation of (A)

Evaporation

(B)

Boiling

(C)

Thermal expansion

(D)

Ideal gas law

The molar mass of a certain gas is 32 moJ-1. The root mean square speed um,, of the gas at 30 oc is (A)

483 ms-1

( B)

(C)

4.83 ms-•

15

152.92 ms-•

(D)

4830 ms-•

804

95.

A thermal nuti·on has a speed v that corresponds to room temperature T = 300 K. What is the deBroglie wavelength of thermal neutron? (A)

96.

98.

14 nm

0.4 A

(Cl

1.4 A

1320 A

(B)

4860 A

1.32 x 10-5m

(C)

(D)

0.1726 A

Calculate the momentum of a photon whose wavelength is 10 A (A)

0 kgms-1

(B)

1.24 x 10-3' kg ms-l

(C)

124 MeV/c

(D)

4.14 x 103 MeV/c

Half wave plate will introduce a phase difference o f - - - - - between ordinary and extraordinary waves (A)

99.

(B)

Calculate Compton wavelength for a proton whose rest mass is 938.3 MeV. (A)

97.

1.4 nm

180°

(B)

90°

(C)

270°

(D)

360°

Diffraction of light can be understood by (A)

Wave nature of light

(B)

Particle nature of light

(C)

Both (A) and (B)

(D)

None of the above

100. The pressure vs. volume graphs for a certain gas undergoing five different cyclic processes shown in Figure. During which cycle (s) does the gas do the greatest positive

D

304

c

B

A

V

E

v

v

(A)

Processes B and D

(B)

Processes A and C

(C)

Process D

(D)

Process E

16

ENTRANCE EXAMINATION FOR ISSION, MAY ~013. M.Tech. (ELECTRONICS)

COURSE CODE: 30.4 Number

:j

L.._ _ _ _ __.

Signature of the lnvigilator (with date)

COURSE CODE : 304 · Time : 2 Hour~;~

Max : 400 Marks

Instructions to Candidates : · 1.

· 2.

Write your Number within the box proyided on the top of this page and fill in the page 1 of the answer sheet using pen. Do not write your name anywhere in this booklet or answer sheet. Violation of this entails disqualification.

3.

Read each question carefully and shade the relevant answer (A.) or (B) or (C) or (D) in the relevant box of the ANSWER SHEET using HB pencil.

4.

Avoid-blind guessing. A wrong answer will fetch you -1 mark and the correct answer will fetch 4 marks.

5.


6.

Do not open the question paper until the start !ligna! is given.

7.

Do not attempt to answe-r: after stop signal is given. Any such attempt will disqualify your candidature.

8.

On stop signal, keep the question paper and the answer sheet on your table and wait for the invigilator to collect them.

9.

Use of Calculators, Tables, etc. are prohibited.

.

1. ..

r

4.

-*

.

· A particl~ of mass of 0.3 kg is subjected to a force F= -kx with k=30Nim. What will be the initial acceleration if it is released from a point 40 em away from the origin?

3x+2y-2=0

(B)

2x +. 3y- 2 = 0

(C)

3x- 2y + 2 = 0

(D)

2x- 2y +2 = 0.

n, a, b

1.588%

(D)

n.

0.0978%

(C)

0.392%

(D)

0.0244%.

(B)

50%

(C)

86%

(D)

100%.

5 PJ

(B)

a capacitor of 10 pF, the energy stored is

10 PJ

(C)

100 PJ

(Ii)

0.01 PJ .

0.3

(B)

0.5

(C)

0.6

(D)

0.8.

In cellular mobile co=unication, the frequency reuse distance D is v3K. R

(B)

vK. R

(C)

v3KR

(D)

vR. 3K.

The noise figure in dB if the minimum receivable signal in a radar receiver is 4.17x10· 14 W with IF bandwidth of 1.5 MHz is 10 dB

(B) . 9 dB

(C)

20 dB

(D)

18 dB.

The beam width between first null of2 m parabolic reflector operating at 900 MHz is (A)

304

(C) · n, a

If the milximum peak to peak voltage ofan·AM wave is 16 mV and the minimum peak to peak voltage is 4 mV, then modulation 'factor is

(A) 11.

(B)

If a potential of 1V is applied across

(A)

10.

n, b

Efficiency of half wave rectifier is

(A) 9.

(B)

Percent resolution of a 10 bit ADC is

(A) 8.

~10~

Given two numbers a and b. Let A denotes the single AM and S denotes the sum of nAMs between a and b, then S/A depends on -

(A) · 45%

7.

(C)40~

(A)

(A) 6.

0015~

If a ~e es through the point (1,2) and cuts the circle x2 + y 2 + 2x + 2y+ 1 = 0 qrthogonally, then locus of its centre is,

(A) 5.

.

is. dipped in water. The water rises up to 8 em. If the .m~.'Ui kejlt in a freely falling elevator, the length of water column in . tht I . iJI' ·... ..;..lm:.,~lie: . .. .XIIFl J~., · ..· (A) sem: .. (B) 10 em (C) 4 em (D) 20 em.

W1~

3.

'

~ 1P CDJ, ~ 1fllt%arY ~lie

'

2.

• \' '· ·,;

20.3'

(B)

21.3'

(C)

2

22.3'

(D)

23.3'

12.

After a target has been acquired, the best scanning system for tracking is (A)

13.

17.

18.

20.

21.

Conical

CD)

Helical.

2

(B)

logw 16

(C)

8

(D)

4.

31,500

(B)

15,750

(C)

262 "h

(D)

525.

USA

(B)

India

(C)

(D)

.

FEM is (A)

Empirical method

(B)

Numerical method

(C)

Analytical method

(D)

None ofthese.

Impedance inversion may be obtained with (A)

A short circuited stub

(B)

An open circuited stub

(C)

A quarter wave line

(D)

A half wave line.

Tropospheric scatter is used with frequencies in the range (A)

19.

(C)

VDE is, EMC standard of (A)

. 16.

Spiral

The number oflines per second in the United States TV system is (A)

15.

(B)

To permit the selection of 1 out of 16 equiprobable events, the number of bits required is (A)

14.

Linear

HF

(B)

VHF

(C)

UHF

(D)

VLF.

The attenuator is used in the Traveling wave tube to (A) . Help bunching

(B)

Prevent oscillations

(C)

(D)

Increase gain.

Prevent saturation

The biggest advantage of the TRAPATT diode over the IMPATT diode is its

.

(A)

Lower noise

(B)

Higher efficiency

(C)

Ability to operate at higher frequencies

(D)

Lesser sensitivity to harmonics.

A tunnel diode is loosely coupled to its cavity in order to (A)

Increase the frequency stability

(B)

Increase the available negative resistance

(C)

Facilitate tuning

(D)

Allow operation at the highest frequencies. 3

304

22.. The Hartley -

Sbann~ ijle 0 re~e~

a limit on the

(A). Highest; fte'ln'\'OY that may be sent over a given channel

(B) M-.inluni cap.ity of a ~el with a given noise level (C) . :Lfa:ritnnm tlumber of coding levels in a channel with a given noise level (D)

23.

Maximum number of quantization levels in a channel of a given bandwidth.

In order to separate channels in a TDM receiver, it is necessary to use (A) AND gates (B) Band filters (C)

Differentiation

(D)

Integration.

24. · The ----------- should lie in the left hili of the S plan for stability (A) Zeros (B) Poles and Zeros (C) Poles (D) None of the above. 25.. · Convert the 101101 Binary number into octal number (A) 65 (B) 55 (C) 51 26.

28.

31.

304

W)4.

NAND and EX-NOR

(B)

NAND and NOR

(C)

AND and X-NOR

(D)

OR and XOR.

The largest negative number can be represented with 8 bits in 2's compliment representation. -256

(B)

-255

(C)

-127

(D)

-128.

(D)

TFF.

Transparent latch is seen in which type of flip flop SR FF

(B)

D FF

(C)

JK FF

Which type of ADC is fastest? (A)

SARC

(B)

Counter type

(C)

Integrated type

(D)

Flash.

The resolution for a DAC is given by 0.4% then no. of bits ofDAC is (A)

32.

~12

(A)

(A)

30.

ro>6

If the output of the gate is always high then the gates applied to this logic are --------and------.

(A) 29.

45.

How many flip-flops are required to construct Mod -12 counter?

W5 27.

(D)

8- bits

(B)

12- bits

(C)

16- bits

(D)

32-bits.

CMRR of an OP AMP is given as 80dB and Ad is 20000.Value of A.m will be (A) 4 (B) 8 (C) 2 (D) 1.

4

33.

34.

35.

36.

Si and Ge lie in ........ block of periodic table (A) III (B) v (C)

IVA

(D)

IV B.

VSWR = 1 is obtained when (A) ZL=O (B) ZL =oo

ZL =Zo

(D)

ZL is reactive.

7 D/h

(D)

7 .\/D.

Half Power beam width of a dish antenna is (A) 70.\/D (B) 70D/h (C)

One of"the following types of noise becomes of great importance at high frequencies. It is the (A) (C)

37.

(C)

Shot Noise Impulse Noise

(B) (D)

Random Noise Transit-time Noise.

A Superheterodyne receiver with an IF of 450kHz is tuned to a signal at 1200kHz. The image frequency is (A)

750kHz

(B)

900kHz

(C)

1650kHz

(D)

38.

A receiver has poor RF selectivity. It will therefore also have poor (A) Blocking (B) Double-Spotting (C) Diversity reception (D) Sensitivity.

39.

Indicate which of the following pulse modulation system is analog (A) . PCM (B) DPCM (C)

40.

PWM

(D)

The code which provides for parity check is (A) Baudot (B) ASCII (C)

2100kHz.

Delta Modulation.

EBCDIC

(D)

41.

The data transmission rate of a modem is measured in (A) bytes per second (B) baud rate (C) bits per second (D) megahertz.

42.

Satellites used for intercontinental communications are known as (A) Comsat (B) Domsat (C) Marisat (D)

CCI'IT-2.

Intelsat.

43.

If the peak transmitted power in a radar system is increased by a factor of 16, the maximum range will be increased by a factor of (A) 2 (B) 4 (C) 8 (D) 16.

44.

Equalizing pulses in TV are sent during (A) Horizontal blanking (C) The Serrations 5

(B) (D)

Vertical blanking The Horizontal retrace.

304

. 45.

A linear block code with a minimum distance dmin can correct up to ------ errors (A) t :S floor[(~~1)12) (B) t?: floor[(dmin-1)/2) (C) t :S floor[dmin/2- 1) (D) t?: floor[dmin/2 - 1).

46.

The mutual information of a channel may be expressed in of the entropy of the channel out"put as (A) l(x;y) = H(y) + H(y/x) (B) I(x;y) = H(y)- H(x/y) (C) l(x;y) = H(y)- H(y/x) (D) l(x;y) = H(y) + H(x/y).

47.

A network which compensates distortion is--------. (A) Filter (B) Equalizer (C) Attenuator (D) Amplifier.

48.

The phase characteristic of a FIR filter is (} (OJ ) = - 5 OJ • The group delay of the filter is (C) -10 (B) -5 (D) 10. (A) 5

49.

Z - Transform, evaluated on its unit circle is --------. (A) DTFT (B) FT (C) IFT

(D)

FFT.

50.

Calculate the critical frequency for reflection at vertical incidence if the maximum electron density is 1.24x106 cm-3 • That would be (A) 5 MHz (B) 7 MHz (C) 10 MHz (D) 12 MHZ.

51.

The maximum efficiency of a full-wave rectifier is -------------------(A) 40% (B) 81.2% (C) 40.2% (D)

90% .

52.

Under normal operating voltages, the reverse current in a silicon diode isabout (A) 1pA (B) · 1mA (C) 10 pA (D) 100 pA.

53.

The Potential at a point due to electric dipole consists of (A) r (B) llr2 (C) 1/r'

(D)

1/r .

54.

If a potential of 1V is applied across a capacitor of 10 pF, the energy stored is (A) 5 PJ (B) 10 PJ (C) 100 PJ (D) . 0.01 PJ.

55.

The work in moving a charge between two points depends on (A) the path (B) Q, E and the path (C) Q and E only (D) Q, E and end points.

56.

Q-Switched LASER is a (B) (A) Continuous Laser (C) . Laser produced by switching operation(D)

304

6

Short burst Laser Low powered Laser.

57.

When a magnetic flux cuts across 200 turns at the rate of 2 wbls, the ipduced voltage is (A) 400 V (B) 100 V (C) 600 V (D) OV.

58.

The Self-inductance of two coil are 4H and 9H. If the coefficient of coupling is 0.5, the mutual inductance between the two coil is (A) 12 H (B) 3 H (C) 6 mH (D) 10 H.

59.

A conductor 1 m long carries a current of 5 mA and is at an angle of 30' with B= 1.5 wblm2• The magnitude of the force is (A) · 7.5 mN (B) 5 mN (C) 3.75 mN (D) 7.5 N.

60.

Ifa wave in free space has E = 2 V/m, His (A) V60 n Aim (B) (C)

120 n Aim

(D)

60 n Aim 240 n Aim.

61.

If the dimension of the narrow and broad walls of a waveguide is 3 em and 4.5 em, the cut off wavelength for the dominant mode is (A) 6 em (B) 9 em (C) 12.5 em (D) 1.5 em.

62.

At low frequencies, earth is a (A) Good Conductor

(B)

Excellent Conductor

(C)

(D)

A Good

A solution to the "blind speed" problem is (A). To change the Doppler Frequency

(B)

(C)

(D)

To vary the PRF To use MTI.

63.

Bad Conductor

To use monopulse

Capacitor.

64.

The largest negative number can be represented with 8 bits m 2's compliment representation is (D) -128. (A) -256 (B) -255 (C) -127

65.

Normalized frequency (V) for a single mode fiber is (A) V ~ 2.4 (B) 2.4 ~ V 9.8 (C) V 2: 2.4

66.

~

3.8.

BW aNA

(B)

BW a 11 NA

(C)

BW a 11(NA)2

(D)

BW a 11(NA)3

Scattering loss in optical fiber varies with wavelength as (A)

68.

0~V

If BW is the bandwidth of an optical fiber and NA is the numerical aperture then (A)

67.

(D)

1/A

(B)

11 }.2

-23 dBm indicates a power of (A) 23 mW (B) 5 ]lW 7

(C)

11 >..•

(C)

-23 mW

. (D)

(D)

11 A3 •

10mW.

304

}

'

of.a

69.

If bandgap ene:r;gy ~~rial ia;l.24 eV then wavelength of peak emission is (A) 1.0 pfu ·· (B) 0.75 pm (C) 1.24 pm (D) 124 p.m.

70.

The material.liiled for optic:81 fiber for least losses is (A) . SiF4 ·(B) NaF4 (C) ZrF4

71.

72.

(A)

'hia11gular device

(B)

Square Law device

(C)

Linear device

(D)

Linear Component.

The informatio11 content of a message with occurrence probability 118 is

75.

78.

(D)

3 bits.

622 Mbps

(B)

622.08 Mbps

(C)

466.56 Mbps

(D)

466 Mbps.

(C)

Conditionally Stable

(D)

Marginally Stable.

(C)

co

(D)

-1.

(C)

1/(s-1)

(D)

11(s-1)·1

Find the Z transform of 6(n) (B)

1

0

Given h(t)= e·• u(t). Find H(s) 11s

(B)

11(s+1)

The TIIP protocol architecture is a result development conducted on network.

of protocol

(A)

Circuit Switched

(B)

Burst Switched

(C)

Packet Switched

(D)

None of the above.

research

Ebi'No is related to SNR, select the correct one from the following. Ebi'No = Es/No

(B)

Ebi'No = NaiSNR

Ebi'No = 11(No.SNR)

(D)

Ebi'No = SNRI No.

(C)

WDM

(D)

OFDM.

(C)

1 dB

(D)

OdB.

What type of approach is Used in DECTI (A)

TDD

(B)

FDD

The gain of an isotropic antenna is (A)

304

114 bits

(B) . Unstable

. (C)

80.

(C)

Stable

(A)

79.

8 bits .

(A)

(A)

77.

(B)

If the closed loop transfer function of a system is 11(s2 + a 2 ) 2 then the system is

(A)

76.

118 bits

In the hierarchy ofSONET, OC-12 data rate corresponds to (A)

74.

NaSiF4.

Photo Detectods a

(A)

73.

(D)

3

dB

(B)

10 dB 8

and

81.

For a short circuited and open circuited line if their impedances are 5 ohm and 20 ohm, then characteristic impedance is (A)

82.

r

(B)

100 ohm

(C)

10 ohm

(D)

25 ohm.

In order to properly reverse bias the collector base junction of silicon transistor, minimum VCErequire\1 is (A)

83.

4 ohm

0.3 V

(B)

1V

(C)

0.5 V

(D).

0.8V.

B is said to be linear if (A)

B and H are parallel

(B)

B and H are perpendicular

(C)

E and Hare parallel

(D)

E and Hare perpendicular.

84.

When the both junction. of NPN diode is reverse biased, then the diode is in which mode (A) Active (B) Cutoff (C) Saturation {D) inverted.

85.

If the voltage or current from the receiving end towards the sending end is decreasing in amplitude with increasing distance from the load then it is called·

86.

I 87.

88.

89.

(A)

Incident wave

(B)

Medium wave

(C)

Reflected wave

(D)

None of above.

Three bulbs of 60 watts each are connected in parallel across 220v, 50 Hz supply. If one bulb burns out (A)

Only remaining two will operate

(B)

Remaining two will not operate

(C)

All of three will operate

(D)

There will be heavy current from the supply.

Two 16:1 and one 2:1 multiplexers can be connected to form a (A)

64:1 multiplexer

(B)

32:1multiplexer

(C)

16:1 multiplexer

{D)

8:1 multiplexer.

A system with gain margin close to unity or a phaSe margin close to zero is (A)

Highly stable

(B)

Highly oscillatory

(C)

Relatively stable

{D)

None of the above.

Human system can be considered as (A)

Open loop system

(B)

Closed loop system with single

(C)

Closed loop system with multivariable

(D)

None of these. 9

304

90.

A system has the trans(er function(1-s)/(l+s); It is known as (A) Low syst.n (B) All system 0

•

(C) . Hi&h system · 91.

. (D)

None of the above.

In a single stage transistor amplifier, if input signal is 1 m V (rms),

RAe

= 2 K ohm,

Rin = 1 K ohm and Beta= 50, then output voltage is (A)

92.

26 tD.V

(B)

50 mV

(C)

75 mV

(D)

100 mV.

If three stage amplifier has individual stage gain of 10 dB, 5 dB and 12 dB, then the total gain is . (A)

12 dB

(B)

(C)

600 dB

27 dB

(D)

17 dB.

93.

A power supply has a voltage regulation of 1%. If the no load voltage is 30 V, then the full load voltage is (A) . 30 V (B) 29.7 V (C) 30.3 V (D) 45 V.

94.

If the input to a differentiating circuit is a saw-tooth wave, then output will be (A)

(C)

Saw-tooth wave Rectangular wave

(B)

(D)

Square wave Triangular wave.

95.

When Vos of a FET changes from -3.1 V to -3 V, the drain current changes from 1 mA to 1.3 rnA, then the value oftransconductance is (A) 30 micro mhos (B) 30m AIV (C) 3 micro mhos (D) 3m AIV.

96.

A unijunction transistor has 10 V between the bases. If the intrinsic stand off ratio is

0.65, then the value of stand off voltage is (A) 6.5 V (B) 0.065 V (C)

10.65 V

(D)

9.35 V.

97.

What is the ratio of modulating power to total power at 100% modulation? (A) 1 : 3 (B) 1 : 2 (C) 2 : 3 (D) 1 : 1.

98.

An FM signal with a modulation index mr is ed through a frequency tripler.

The wave in the output of the tripler will have a moduiation index of (A)

99.

mr/3

(B)

mr

(C)

3 mr

(D)

9 mr.

How many NAND gates are needed to realize OR gate? (A)

1

(B)

2

100. If the signal level is 1 mW, power gain is (A) 0 dBm (B) 1 dBm

10

(C)

3

(D)

4.

(C)

0.01 dBm

(D)

10 dBm.

ENTRANCE EXAMINATION FOR ISSION, MAY 2010. Ph.D. (ELECTRONICS AND COMMUNICATION ENGINEERJNG) COURSE CODE : 138

Number:

L'------'

Signature of !he l11vigi/atur (with dale)


Max : 400 Marks


Write your Number within the box provided on the top of this page and fill in the page 1 of the answer sheet using pen.

2.

Do not write your name anywhere in this booklet or answer sheet. Violation of this entails disqualification.

3.

Read each question carefully and shade the relevant answer (A) or {B) or (C) or (D) in the relevant box of the ANSWER SHEET using HB pencil.

4.

Avoid blind guessing. A wrong answer will fetch you - 1 mark and the correct answer will fetch 4 marks.

5.


6.


7.

Do not attempt to answer after stop signal is given. Any such attempt will disqualifr your candidature.

8.


9.

Use of Calculators, Tables. etc. are prohibited.

1.

Semiconductors are those which have (A) no physical distinction between the two bands (B) an empty conduction band and a filled valence band (C) current due to electrons only (D) current due to holes only

2.

Input resistance of an ides! voltage and current amplifier is (A) 0. 0 (B) 0, infinity (C) Infinity, 0 (D) Infinity, infinity

3.

The high frequency response of an amplifier is determined by its (A) Hybrid 1t model (B) Hybrid T model (C) Cascade model (D) Eber Moll's model

4.

Q factor of an inductor is given by

(A)

mL

(B)

(C)

6)L/R

rff.LR

(D) mLR

5.

Avalanche breakdown occurs when (A) forward current becomes excessive (B) tbe potential barrier is reduced to zero (C) forward bias exceeds a certain value (D) reverse bias exceeds a certain value

6.

Ii' the de value of a rectified output is 300 V and pesk to peak ripple value is I 0 V. the ripple factor is (A)

7.

8.

9.

(B)

3%

(C)

40.6%

(D)

90%

A PN PN device having no gate is called (A)

UJT

(C)

Rectifying diode

Free wheeling diode (D) Shockley diode (B)

The Kirchoff a law fails in (A) Linear circuits (C) 'Dual circuits

NonlineHr cirouits (D) Distributed parameter circuits

(B)

Condition of reciprocity of network (A)

138

1.18%

y"

=;y'l3

(B)

z,i

&

~~

(C)

2

A=D

10.

11.

Transformer coupling in transistor amplifier circuits provides high efficiency because (A)

flux Jmkages are incomplete

(B)

collector voltage is stepped down

(C)

collector voltages is stepped up

(D)

de resistance is low

When an opamp is operated in common mode fashion, its CMRR should be (A)

12.

16.

I 6.

17.

slight.ly lesser

(B)

(C) Infinity

(D)

- - - - - than that of

greater

(C)

equal to

(B)

Photoemissive cell

(D)

20 db non-invarting 10 t1mes

(D) Photovoltaic cell

Photoconductive cell

In Gunn diode, negative resistance is obtained because o£ (A)

Avalanche breakdown with high voltage gradient

(B)

Electrons domains are formed at the junction

(C)

Electron transfer to a less mobile energy level

(D)

Tunneling effect across the junction

The tunnel diode (A)

has a tiny hole for tunneling

(B)

has a point with high reverse resistance

(C)

uses a high doping level to provide a narrow junction

uses an alloyed junction for tunneling

A parametric amplifier has an input and output frequency of 2.6 GHz, it is pumped at 6GH~. rt is a (A)

Backward amplifier

(B)

(C)

Doubler amplifier

(D) Travelling wave amplifier

Degenerate amplifier

Light emitting diodes fabricated from Ga As emit radiation in the l'egion of (A)

18.

10 db

Solar cell is basically a (A) Photometer (C)

14.

(B)

The gain of inverting amplifier is amplifier using identical op-amps. (A)

13.

Zero

Green

(B)

Infra red

(C)

Ultra violet

(D) Visible

Temperature ooefficient of re5istance of sensitor is (A)

Negative

(B)

Positive

(C)

3

Zero

(D)

Large 138

19.

20.

Capacitors for ICs can be fabricated using (A)

Isolation process

(B)

Integrators

(C)

Masks

(D)

Si02 as dielectric

(C)

oll(s 2 + o~}

Laplace transform of Cos cut is {A)

21.

22.

26.

28.

138

+ m2)

(D)

s~/(s~ +

(B)

cosine only

(C)

both sine and cosine

(D)

neither sine and cosine

(C)

Z I (Z-1)'

Z transform of a step input function is (B)

1

Z/(Z·l)

(D)

Z(Z-1)~

For a decade counter, number of RS fliptlops lobe used in cascade are (B)

10

2

(C) 4

(D) 5

In a RS flip flop no change in state will occur due t o - - - - - - input. 0-1

(B)

1-0

(C)

(D)

0-0

1-1

Emitter coupled logic exhibits fastest switching speed because the gates use (A)

Saturated transistors

(B)

Saturated diodes

(C)

Thyristor

(D)

Unsaturated transistors

A computer having 4K memory means ------storage locations. (A)

27.

s/(st

sine only

(A)

25.

(B)

(A)

{A)

24.

+ uil)

In the Fourier series expansion of an even function there are

(A)

23.

a)l'(s2

4

(B)

400

(C)

4096

Demorgan's theorem can be expanded to three variables as (A)

(X+Y+Z)' =-(XY)' +(YZ)' + {ZX)'

(C)

(X+Y+Z)'

=XYZ

(B)

(X+Y+Z)' =X'+ Y'

(D)

(X+Y+Z)'

+ Z'

=X'Y' Z'

The three variable Boolean expression f =1: 0, 1, 3, 4 means A'B'C' + A'BC' + A'BC + ABC

(A)

A'B'C' + ABC' +ABC

(B)

(C)

A'BC' + AB'C' +ABC+ A'BC

(D) A'B'C' + A'B'C + A'BC +ABC'

Cifl)

29.

Binary 1100101 is equivalent t o - - - - - - in Gray code. (A)

30.

32.

33.

34.

35.

36.

1010011

(C)

0010111

(D)

0100101

4

(B)

(C)

l/4

1

(D) 0

An exclusive OR gate can be realized by using {A)

2 OR gates

{B)

(C)

-! NAND gates and one NOR gate

(D) 5 NAND gates

2 NOT gates and one OR gate

An example of a combinallonal circuit is (A)

Counters

(B)

Shift s

(C)

Full adder

(D)

Flip flop

ln Moore sequenttaJ machine the output is a function of (A)

all the inputs

(B)

all the present states

(C)

all possible combinations o£ input and present states

(D)

a few combination or inputs and prestmt state

The ROM consists of

(A)

a multiplexer followed by a decoder

(B) a demultiplexer

(C)

a multiplexer

(D)

a decoder followed by an encoder

Shift of a by one bit to the left is equivalent t o - - - - - by 2.

(A)

Addition

(B)

(C)

Multiplication

(D) Division

For a four input re'iil;tan.ce divider having 0 voltage for a digital input of 1101 is (A)

37.

(B)

In a four input NAND gate all inputs are 1 the output is (A)

31.

1100101

1.5V

{B)

5V

Subtraction

=0 V, 1 == +15 V the analog output

(C)

11~

(C)

TTL

V

(D)

13V

Least propagation delay is exhibited by (A)

ECL

(B)

HTL

5

(D) RTL

138

88.

The function of two parallel switclles. is similar to logic gate which is

(AJ 89.

46.

47.

X+X'

=1

(B)

X.X=X

(C)

LX= 1

(D) O.X=O

1

(B)

0

(C)

X

(D) X'

XY'Z'

(B)

'X:Y'Z'

(C)

X'(Y'+Z1

(D) X{Y'+Z1

CMOS

(B)

DTL

(C) ECL

(D)

TIL

a =~

(B)

a = nefi

(C)

a = efi

(D) a=

t ne11J

1..= hmv

(B)

(C) l..=h/ m

J..=hl mv

(D) 1..: 2

1t I

hm

The conductivity of a conductor can be increased by (A)

increasing its temperature

(B)

decreasing its temperature

(C)

increasing its vibrations

(D)

decreasing its temperature and vibrations

The value of elm of an electron is (A)

1.758 X 10" C/Kg

(B) 1.601 X ltr' C/Kg

(C)

3.62 X 10-ll C/Kg

(D)

5.613 X 109 C!Kg

{C)

8.1

The relative permittivity of silica ie (A)

138

OR

De Broglie wavelength A. of an electron relates to Plank's constant h and mass of electron m as (A)

45.

(D)

The electrical conductivity a is related to mobility 11 by (A)

44.

NOR

Family of 7400 series of digitallC is (A)

43.

(C)

The complement of (X + yz + XY) will be (A)

42.

NAND

The Boolean expression XY(X'YZ + XY'Z + X'Y'Z') will be simplified as (A)

41 .

(B)

Pick out the invalid relation according to Boolean algebra (A)

40.

AND

1.006

(B)

4.5

(D)

3.8

6

I

48.

Dipole moment per unit volume is called

(A) (C) 49.

Electric flux density Charge density

The relative permeability of a medium space llo as

jl,

(B)

Magnetic flux density

(D)

Polarization

is related to its own permeability of free (C)

60.

A sphere of 10 m encloses a charge of 1000 coulombs the displacement density is given in c I m2 by (A)

51.

6 3.

100

(B)

10,000

(C)

0.834

(C)

J = cr E

(D)

1.667

Select the equation which is not Maxwell (A)

62.

!1. llo =II

D

=E E

(B)

E =ED

For normal incidence the angle of incidence is (A) 90 (B) 180 (C)

0

CD) 46

When a wave is incident from a more dense into a less dense medium at an angle equal to or exceeding the critical angle. the wave will have (A) Total internal refraction (B) Total interval transmission (C)

Total internal reflection

(D)

Surface wave

54.

The phase velocity of a transmission line in of its R. L , C and G pa.r ameters is (A) V= IJR (B) V= 1/LC (C) V = 1/(LC)m (D) V=GCIRL

55.

VSWR of a transmissiOn line is defined as

56.

(A)

Vmax /Vmin

(B)

Vmin I Vmax

(C)

Vmax. Vmin

(D)

1 /
For a reflection coefficient of 0.5 the value of SWR is

CA> o.s 57.

(B)

o

(C)

1

(D)

3

A line of characteristic impedance 100 ohm is terminated by a 100 ohm impedance. The input impedance will be (A) Zero (B) 10 ohm (C) 50 ohm (D) 100 ohm 7

138

58.

59.

The directive gain in a given direction is the ratio of (A)

Radiation intensity in that direction to the total input radiated power

(B)

Average power to maximum power

(C)

R.M.S. power to peak power

(D)

Radiation intensity in that direction to the average power radiated

One among the following is a non resonant antenna (A)

Rhombic antenna

(C) Adcock antenna 60.

61.

(B)

Small circular loop

(C)

Helical

(D)

Yagi uda

When microwave signals follow the curvature of the earth, this is known as Faraday effect

(B)

Ducting

(C)

Ground wave

292 ohms

(B)

73 ohms

(C)

146 ohms

(D)

50obms

In a communication system, noise is most likely to affect the signal

at the transmitter

(B)

in the channel

(D)

in the receiver

The advantage of AM over FM 15 (A)

SNRissmall

(B)

Lower bandwidth requirement.

(C)

Less modulating power

(D)

More useful t:ransmitted power

The advantage of DSB over SSB full carrier AM is (A) less available channel space

138

(D) Troposcatter

The radiation resistance of a folded dipole antenna is

(C) in the information source

65.

Log periodic antenna

Parabolic reflector

(A)

64..

(D)

(A)

(A)

63.

Yagi antenna

An antenna that is circularly polarized is

lA) 62.

(B)

(B)

signal is less resistant to noise

(C)

more stable transmitter circuit gives better reception

(D)

more power to transmit same signal.

66.

The frequency deviation in a PM tr!UlJ!mitter having modulation index. 6 is 60KHz. its bandwidth is (A)

67.

68.

69.

71.

72.

(B)

360 .l{}h

(C)

10KHz

(D)

140KHz

The term neutralization refers to (A)

Inhibiting spurious oscillations

(B)

Stabilizing the frequency of an oscillator

(C)

Modulating at very low levels

(D)

Tuning an antenna for maximum gain

The Hartley law states that (A}

the maximum rate of information transmission depends on the depth of modulation

(B)

the maximum rate of information depends on the channel bandwidth

(C)

only binary codes may be used

(D)

redundancy is essential

An FM stgnal with a modulauon mdex mr is ed through a trequency tripJer. The wave in the output of the triplet will have a modulation index of (A)

70.

60KHz

mr/9

(C)

mr

ID)

3 mr

In the spectrum of a FM wave (A)

the carrier frequency disappears when the modulation indelt Is large

(D)

the amplitude of any side band depends upon the modulation index

(C)

the total number of sidebands depends upon the modulation index

(D)

the carrier frequency cannot disappear

Pulse width modulation may be generated (A)

by differentiating a PPM signal

(B)

by a monostable multi vibrator

(CI

by integrating a PPM signal

(D)

by a bistable multi vibrator

(C)

PWM

Quantizing noise oocurs in rA)

TDM

(B)

FDM 9

(D) PCM

ISS

73.

Companding is used (A)

in delta modulator t~ combat noise

(B)

to protect smlill signals in PCM from quantizing distortion

(C) in PWM for working it with TDM (D) 74.

in PCM to reduce SNR

1n superheterodyne receivers, the signal voltage is combined with local oscillator in 8 mixer and converted to a lower fixed ~ency whicll is amplified and detected to

produce the original information. This fixed frequency is called 8S

76.

(A)

Internal frequency

(B)

Intermediate frequency

(C)

International frequency

(D)

Image frequency

A scheme in whicll several channels are interleaved and then transmitted together is known as (A)

76.

78.

80.

(B)

(C)

D-bit

(C)

=W(l + SNR)

C

(C)

C = W log(1 + SNR)

super group

(D)

multiplexing

Redundancy

(D) Reliability

(B)

(D)

=W I (1 + SNR) C =W /log(l + SNR)

C

The entropy for tossing a coin i s - - - - - - bitJmeasage. 2

(B)

t

(C)

0

(D)

1

Coherent detection employs - - - - - - o f carrier envelope. (A)

Amplitude

(B)

Phase

(C)

Phase and frequency

(D)

Amplitude and frequency

lf it takes the transmitted signal 2 m sec to go to the target and come back aftetreflection the target is at a distance of kilometres from the radar. 30

(B)

100

(C)

150

(D) 300

(C)

low pllBs

(D) high

A wave guide is a - - - - - - filter. (A)

138

D-entropy

(A)

(A)

81.

subgroup

Hartley Shannon law is expressed in bits per second as

(A)

79.

(B)

A sequence of symbols which are dependent upon one another is called (A)

77.

group

mechanical

(B)

band 10

82.

83.

A Klystron a cavity acting as a buncber and catcher works on tbe pnnciple of (A)

Velocity modulation

(B)

Frequency modulation

(C)

Guiding waves

(D)

Impedance transformation

(C)

4-SGHz

The range of X band is (A)

84

87.

88.

89.

91.

2·4 GHz

(D) 8-120Hz

Data link

(B)

BPSK

(C)

(D) GMSK

QPSK

layer is concerned with local delivery of frames between devices (B)

Transport

(C)

Network

NF

(D)

Physical

Noise figure is related to noise factor a.& (A)

NF=I~F

f8)

(C)

NF = 10 log10 F

(D)

=log F NF =20 logiO F 10

When through the occurrence of event A, the event B cannot take place and vice versa. the events A and B are said to be (A)

Exclusive

(B)

Independent

(C)

Mutual

(D)

Mutually exclusiv~>

In a Delta Modulation the granular noise occurs when the modulating signal (A)

decreases rapidly

(8)

increases rapidly

(C)

remains constant

(D)

remains idle

A 10 GHz signal was beamed up at a geostationary satellite at a distance of 36000 km from the signal undergoes a free space loss of (A)

90.

FSK

The on t.he same LAN. (A)

86.

(B)

The modulation technique used in GSM system is (A)

85.

1-2 GHz

10 db

{B)

20 db

(C)

200 db

(D) 365 db

For frequency f and distance D. the free space attenuation of a RF signal is equal to (A)

20 log 10 (D I f)

(B)

20 log 10 D + 20 log 10 C

(C)

32.5 log10 (D f)

(D)

32.5 log 10 D + 20 log111 f

(C)

Vacuum

Sound travels faster ID (A) Air (B)

Aluminium l1

(D)

Water

138

92.

If the absolute power ratio is 10,000, the power gain in db is (A)

93.

94.

99.

10 db

(B)

3 x 10~ 16 watts

(C)

5 x 10-16 watts

(D)

1 x 10-14 watts

(D)

TOM

(B)

FDM

(C)

WDM

(D) SDM

The most commonly used ISM band refers to the frequency range 1.2-2.2 GHz

(B)

2.4- 2.5 GHz (C)

5-6 MHz

(D)

TO- 12 MHz

(D)

75 ohms

(D)

128 Kbps

- - - - - - is the characteristic impedance of free space. 478 ohms

(B)

377 ohms

(C)

50ohms

What is the line speed of a PCM system for voice transmission? 8 Kbps

(B)

32 Kbps

(C)

64 Kbps

A - - -- --is a make before break process in mobile communication.

(A) bard handoff

(B)

soft bandoff

(C) strict handover

(D)

turbo handover

SDH is the name of (A)

Wireless standard

(B)

LAN standard

(C)

Optical network standard

(D)

Microwave standard

100. UMTS employs------ as the air interface.

138

40 db

is a process by which different information sources are propagated on an optical fibre by modulating lasers at different wavelengths.

(A)

98.

(C)

4 x 10~17 watts

(A) 97.

1 db

(A)

lA) 96.

(B)

For an electronic device operating at temperature of 17 C and bandwidth 10 KHz. Determine the thermal noise.

(A)

95.

4 db

(A)

FDMA

(B)

TDMA

(C)

CDMA

(D)

Wideband COMA

12

ENTRANCE EXAMINATION FOR ISSION, MAY :lOll. Ph.D. (ELECTRONICS AND COMMUNICATION ENGINEERING) COURSE CODE : 138 Num ber:

I

L...-_

_ __ J

Signature of the lnvigilotor (with date)

COURSE CODE : 138 Time : 2 Ho urs

Max : 400 Marks


2.

'

Write your Number withi n the box provided on the top of this page and of the answer sheet using pen . Do not write your name anywhere in this booklet or answer sheet. Violation of this entails disqualiftcation.

em in th e page l

3.

Read each question carefully and sh.1de the relevant answer {AI or cB) or or (D) in the relevant box of the ANSWER SHEET using HB pencil.

,~_

Avoid blind guessing. A wrong answer will fetch you -1 mark and the correct answer will fetch 4 marks.

5.


6.

Do not open the question paper until the start :signal is given.

7.


8.


9.


(C)

1.

If e,

=2

(A)

1

fo1• a dielectric medium, its electric s usceptibility is (B)

(C)

2

3

(D)

2

•o ~.

2.

3.

The magnetic field in an ideal conductor is (A)

Zero

(B)

(G)

Finite

(D) The same as its outside field

The intrinsic impedance of the medium whose a= O,e, =9 and flr = 1 is (A)

4.

9.

10.

~rO

(D)

60 ;c 0

(B)

(C)

20m

30m

(D)

25 rn

polarization is used fo1· high frequency applications

Lineru·

(B)

Ci.J·c111ar

(C)

Elliptical

(0)

Horizontal

0.1 Hz

(B)

0.2 Hz

(C)

1Hz

(D)

2KHz

15m

(B)

150m

(C)

L5 Km

(D)

75 m

11' the target cross-section is rapidly changing the best choice for accurate tracking is

lAl

MonopuJ se tracking

(B)

Conical scan tracking

(C)

Lobe switching

(D)

Sequent-iallobing

A radar in which the radar beam is steered electronically is (A)

Tracking radar

(B)

MTI t·adar

(C)

Phiise a nay radar

(D)

SAR

A SAR operating at lOG Hz uses an anteu:oa whose effective aperture is 5m. Hs cross range resolution would be (A)

138

120

A pulse compression radar is ope1·ating with expanded and compressed pulse widths of 5f!S and lOOnS respectively. Its range resolution is (A)

8.

(C)

A ship sailing at a radial speed of 10 mls towards an HF radar operating at 3 l'vlliz would produce a Doppler shift of ( A)

7.

10m

By far--- -(A)

fl.

(B) 9 o

40~r0

The wavelength of a wave with a propagation constant 0.1 rr + j 0.2 rr is (A)

5.

Infinite

2.5 rn

(B)

(C)

5 111 2

10m

(D)

15m

..

11.

A basis vector for a vector space V may be defined as a set of vectors in V which (A)

are mutually orthogonal

(B)

are linearly independent

(C)

span the space V

(D)

are linearly independent and span the space V .f'l •I

[2,

'!'he value of J cos aJt o(t)dtis - -- --

where o(t) denotes

,'f"/4

(A)

13.

0

(B)

1

(C)

n/4

,fi

(D)

A signal x(t) has energy E. '!'hen the signal x(at), a>O, has an amount of energy given by (A)

14.

15.

=

2

z

1

-

0

(C)

a 2E

(D)

E/a2

(C) 130

z ,

~z- ~

1

(D)

65

(D)

l

and x{n) is right sided sequence ~hen x(3) is (B)

2

(C)

-l

If X(k\ is the k-th OFT r.oefficient of a discrete sequence x(nl of length N whoE" qampling frequency is Fs then X(k) cc.rre.sponds to a frequency of (A)

17.

Efa

(B) 350

175

If X(z) (A)

16.

(B)

A signal x(t) 5cos(240nt) was sampled al a frequency F,. The signal recovet·ed from the samples was, however, found to be 3cos(l10Jtt). '!'he sampling frequency F, is equal to samples per second. (A)

,

aE

(B)

kF, 2N

(C)

--· 2kF N

(D)

kF, N - 1

An LTI system has a gain independent of frequency and produces a time-delay of~

seconds for all frequencies. Wllich of the following statement is true? (A)

It produces phase distortion

(BJ Its phase-shift versus frequency relationship is linear

18.

(C)

It produces a constant phase-shift for all Frequencies

(D)

None of the above

If x(n) is of finite duration and bas N samples, t:hen its autocorrelation rnlk) will have

a duration of (A)

2N

samples. (B)

N2

(C)

3

2N-l

(D)

2N+l

138

19.

The discrete time LTI system described by the difference equation y(n) + a,y(n-1) + a2y(n-2) = x(n) is stable if (A) (C)

20.

Ia2l Ia•l

< 1 , I ad < 1+ a2

(B)

Ia, I < 1, Ia2l

< 1, Ia2l < 1+ at

(D)

none of these

What should be the cut-off frequency of the low filter shown in the following multirate digital signal processing system? .. 1

(A)

21.

23.

2~.

1t/5

(B)

LPF

ru7

(C)

1!/35

(D)

121li35

The minimum number of mu ltipliers required to realize an FIR filter with system function H{z) 1+2 z· 1 + (3/2) z·2 + 5 z·3 + (3/2)z-4 ~ 2z·• + z·• is

=

{A)

22.

< 1

7

(B)

4

(C)

8

(D)

3

The transform which possess the 'multi-resolution' property is transform. (A)

Fourier

(B)

Short-time Fourier

(C)

Cosine

(D)

Wavelet

For an 8-bit image x(m,n), the transformation y(m,n)=255 -x{m,n) will yield (A)

a dark image

(B)

a bright image

(C)

negative of x(rn,n)

(D)

same as x(m,n)

The wavelet coefficients of an image after second-level decomposition is shown below:

16

7

12

10

-7

8

8

'1

4

-3

4

·3

2

-2

-2

0

The imtial threshold required for encoding and decoding of an image usmg BZW algorithm is {A)

25.

138

8

(B)

16

(C)

32

(D)

64

An analog signal bandlimited to 10KHz is sampled at Nyquist rate and quantized to 4 levels of a PCM system with probabilities !h , ~ , 118 and 1/8. The rate of information transmission is (A)

35000 bits/sec

(B)

17500 bits/sec

(C)

52500 bits/sec

(D)

70000 bits/sec

26.

The length and the Impedance of a quarter wave transformer to match 90 ohms source with 40 ohms load in a dielectric substance of dielectric constant 4 at 3 GHz are (A) 1.25 em and 40 ohms (B) 2.5 em and 40 ohms, (C) 1.25 em and 60 Ohms (D) 2.5 em and 60 ohms

27.

TEM wave propagating in y direction has (A) Ey= Hy =0 (C)

28.

29.

(A)

Stri pline

(B)

Coplanar waveguide

(C)

Slot line

(D)

FINline

The minimum and maximum values of the VSWR is (A) 0 and infinity (B) 0 and 1

32.

33.

(D)

- infinity and infmity

(B)

Transverse components ofEH are ZERO Transverse components of EH are NON ZERO

(C)

Longitudinal components of EH are zero

! D)

None

Shorted 118 wave length transmission line Oossless) acts as (A) Il\rnUCTOR (B) CAPACITOR

(C) RESONATOR

(D) None

S Band of frequency range is (A) 1·2 GHz (13) 2-4 GHz

(C)

1/8 WAVELENTH transmission line matches (A) (3 + j4) ohms source to 5 ohms load (B) (C)

34.

1 and infinity

Microstrip line is said to Quasi TEM mode because (A)

31.

(D)

Ey=By =Non zero Ey=O,Hy=l

The planar transmission line that s pUl·e TEM mode is

(C)

30.

Er-Hy=l

(B)

(3 + j4) Ohms source to 4 ohms load

(D)

4·8 GHz

(D) 8·12 GHz

(3 + j4) ohms sow·ce to 3 ohms load None

The capacitance with and without a dielectric materi.al inside a plana1· transmission line are 8 m1ero farads and 2 microfarads respectively. 'l.'he effective dielectric constant is (A) 4 (B) 2 (C) 16 (D) None 5

138

35.

36.

37.

Conformal mapping technique belongs to (A)

Quasi static Ana lysis

(8)

Full wave analysis

(C)

Hybrid analysis

(D)

None

lf the VSWR is 1 at tbe inpul port of a microwave component then (A)

Sll =0

(C)

S 11

42.

43.

(B)

101/99

Magnetron

(B)

'l'W'f

TRUE

(C)

9111

(D)

l!f9

(C)

Klystron

(D)

Gunn diode

(B)

0.2

(B)

0.5

(C)

(AI

The frame is tmmediatelr resent

(81

:\jam signul is .;ent by the station

(C)

The backoff value is set to zero

(D)

The backoffvalue is decremented by 1

FALSE

0.66

(D)

0.3

On a network that uses Network addresti translation. - -- -- has translation table (A)

Swit~h

(B)

Router

((')

Server

(D)

None of the above

(C)

class C

Tdentify the class oflP uddress 191. L2.3 class A

(B)

class B

(D)

class D

The simple mail transfer protocol utilizes----- t.o send its mudule to another host (A)

138

99/101

\Vhen a collision IS dt!tected in a network usm~ CSl\WCU.

(A) 44.

None

A transmission line having the characteristic impedance of 100 ohm,; is termlnated with a load impedance of 150 ohms. The load re£1cction coefficient is given by (A)

-II

(D)

All three ports of an ideal lossless reciprocul waveguide component can be MATCHED (A)

.JO.

Slt=l

'PUSHING' is a phenomenon in (A)

39.

=infinity

(B)

Sl 1 of an ideal transformer of turns ration 10: I is (A)

38.

-

T

(B)

(C)

UDP 6

D~S

(D)

ARP

..

45.

Spread spectrum LAN makes use o f - -- -- frequency range (A) 5.5 t.o 5.575 GHz (B) 18.825 to 19.205 GRZ (C) 2.4 to 2.48 GHz (D) 9.25 to 12.25 GHz

46.

Access network is running between (A) end s (C) route1·s and gateways

(DJ

routers end s and edge router>.

Datagram mode of transmiss-ion ensures (A) Reliable data transtn.i ssion (C) Real time transmission

(B) (D)

Sequential order tTansmission All of thB above

l

-1-7.

(B)

48.

In the transmission structure of ISDN the D channel (A} carries channel signaling information (B) carries high speed data signals (C) ing both control and data signalhtg ffi) canies only low speed digital signal

49.

The basic channel structure ofiSDN consists of (A) Two full duplex 64kbps B channel (B) Two full duplex 16kbps D chaDJJ.e] (C) One D chanuel at 64 kbps (D) L55 mups r11te Band D channel

50.

The Frame relay transmission is ed in (A) X.25 network tB) ATr-f r1el.worl< (D ) Syste m nE-twork mchitecture SNA (C) Internet

51.

ATM adaptation lay,•r t)•pe 2 s
( Cl (D)

constant bit rate services variable bit rate services both (A) and (B) reduced transmission overhead services

52.

The SDH level 4 s-- - - - bit -rate (A) 155.52 Mbps (BJ 3-1.3615 Mbps (C) 622.080 :Vfbps (D) 1.5-U Mbps

53.

The world w-ide standard for the digital transmission network is (A) Plesiochronous digital hierarchy (B) Synchronous digital hierarchy (C) Synchronous optical network (D) None of the above

54.

The IGiVIP protocol is used in

(A)

(C)

Errorreporti ng Address resolution

(D) (D) 7

Multicast rout.ing Congestion and flow control

138

55.

An example for hash funcLion is (A) (C)

56.

message digest cyclic redundancy checks

(D)

checksum all of the above

...

A bridge has access to t h e - - - - - address of a station on the same netw01·k (A) network (B) physical (C) router (D) none of the above is the collection of protocols that provide security at the TP layer level

57. (A)

58.

(B)

'l'LS

(B)

SSH

(C)

PG P

A method to provide for the secure transport of email is called (A) TLS (B) SA (C) PGP

(D)

Ipsec

(D)

lpsec

59.

- - - - - i s the control protocol that adds functionalities to the sb·eaming process (D) SfP (A) RTSP (B) HTTP (C) T/IP

60.

A DNS response is classified as - - -- - if the infot·mation comes from a cache memory (A) authoritative (B) unauthoritative (C) iterative (D) recursive

61.

An antenna of impedance 45·jl0 n is directly connected to a 50 The matching e fficiency is (A) 90% (B) 100% (C) 98.6%

Q

transmission line. (DJ

92%

62.

A power of lOOW is radiated from an isotropic radiator. The "))Ower radiated per unit solid angle ana power density at a distance of 10 km from the antenna are respectively (A) 25 W, 10 W (B) 25/ 1t W, 25/100 1t W (C) 7.96 W, 0.08 JJ W (D) 0.08 p W, 7.96 W

63.

An antenna is to be used from 60 to 65 Hz. Its length has been cut for 60 Hz. The tuning element needed is (B) An adjustable inductor (A) An adjustable capacitor (D) Any of the above (C) A variable resistor

64.

The input impedance of an end fed Hertz antenna is (A) 1000 Q (B) 73 Q (C) Depends on length (D) 300 Q

138

8

65.

Two isotropic antennas are separated by a distance of two wavelengths. If both antennas are fed with currents of equal phase and magnitude, the number of lobes in the radiation pattern in the horizontal plane is (A)

2

(B)

4

(C)

6

(D)

R

66.

A TV transmitting aerial is fixed on top of a 150m tower located on a mountain of 1200m h1gh. The range of the transmitter in Km is (A) 152 (B) 51 (C) 0.152 (D) 0.03 l

67.

An antenna has again of 40 tLB at a frequency of 300MHz. The effective urea of t.be antenna in m2 is (A) 796 (B) 10• (D) 3183 lC) 2500

6!l

A low frequency transmitting antenna has a radiation resistance of 0.2 n and u loS£ resistance of 1 n. If the current fed into antE: rel="nofollow">nna is 50A the radiated power in W is (A) 500 (B) 2500 (C) 3000 (D) 10

69.

fn a step inex fiber, what is the cut-off frequency of the LPu mode? (A) 0.0 (B) 2.405 (CJ 3.832 (DJ

5.520

70.

'T'wo :oiogle mode fibers with MFDs of 1011m and 9ft m are spliced. What is Lbe splice lvss in dB? !A) 0.048 (B) O.z..t (CJ (D) :3

71

With an OTDR, it is possible to know
The {JVeTall link IL•ngth All of the above

72.

The material for making an efficient LED ;.hould be
7.3.

'l'he highest wavclengt.h that silicon c:11n ubsorb is 1.12ftm.. What is the appromnnte bandgap of S i? (A) l.1 eV (B) 1.4 eV (C) 1.7 eV (D) 2.3 eV

74.

Which wavelength is most suitable for pumping an EDFA? lA) 0 85f.lm (B) 0.98 11m (C) 1.30 111n

75.

(D)

1.•35 J-IID

Which of the following process is used to rompensate for the GVD-indured di~perston in a Soliton? (A) FWM IB) SPM (C) M (D) All of the above

9

138

76.

Silicon diodes are preferred to germanium diodes for high temperatwe operation because \A) Doping of silicon is a simple process (B) Rate of increase of reverse saturation current with tem perature is more in the case of silicon (C) The reverse saturation current of silicon diodes is smaller thaJJ that of germanium (D) Silicon diodes can be used to rectify even very small voltages.

77

The frequency of ripple in the output voltage of a 3¢ half controlled bridge rectifier depends on the (A) Firing angle (B) Load inductance (C) Load resistance (D) Supply frequency

78.

The switching speed of a P·N junction having a heavily doped P region depends primarily on (A) The mobility of minority carriers in the P region (B) 'The lifetime of minority carriers in the P region (C) The mobility of majority carriers in theN region (D) The lifetime of minority carriers in theN region

79

Due Lo illumination by light, l.h e electron and hole concentrations in a heavily doped n type semi-conductor increase by fl. TJ and fl. p respectively. rr u ; is the intrinsic concentration, then

80.

81.

(./\)

t. n < t. p

IB)

/In rel="nofollow"> ,\ p

\C)

C. n

=

(0)

fl. n >< ~ p = nf'

Whlln a reverse bias is applied to the Gate of JFET the depletion region width (A) Is uniform in the channel (B) Is wider near the source and tapers near the drain (C) Is wider near the drain and tapers near the source (D) Is nil The temperature of a silicon transistor is increased from -55"C to 175•C. Theo (A) L:o increases, fJ decreases, VaE decreases (B)

1.. decreases, j3 decteases, Vsa decreases

(C)

1,0 increases.

(D)

82.

138

6 p

fJ increa-'>es, VnE increases Teo incr·eases, fJ increases, VnE decreases

ln a class B push-pull amplifier Vcc=25 volts pek voltage output amplitude Vm= 16 volts; RL 8 ohms. The de power Pdc supplied is given by (A) 10 wa~~~ (B) 16 watts (C) 20 watts (D) 32 watts

=

10

-

=

83.

A Cl:: amplifier with un byed emitter resistor R! 0.1 Kohms has a collect.or load He=- 6 K ohms hfe=99 and lrie = 1 K ohm. Tbe best esnmate for Avis given by (A) 45 {B) 50 (C) 99 (D) 4!15

8-~.

An amplifier vo.-ith midband gain A = JOO has a negative applied of value p =l/100. Given the upper cut-otl' without was 60 KHz. wi~h rccdback it becomes (A) 10 KH~ (B) 12 Kliz (C) 300 KH~ (Dl 360KHz

85.

A miller integrator has an aiming poLcnl.iul o[ 30 volts. The sweep voltage blt tbc output i;, 10 volt-a. The open loop gain of the OP amplifier is 104. Tbc pl!rcentage sweep error is then (A) l/3 (B) 3/100 (C) 1/300 (Dl 3/300

86.

A rertam Jl{ FF has propagation delay of 12ns The largest ~!OD counter lbut can hoe constructed from these FFs and still operate upto 10i\IH2 is (Al Any (B) 8 (C) 256 (Dl 10

87.

With wluch decoder is it possible to obtain runny code conversions? (A) 2 Line to .J line (B) 3 line to 8 line (C) :-lot possible with any decode1· (D) 4 line to 16 line dccodAr

88.

How many microseconds it will take to I rac1sfer an 8-bit data intu 11 serial-in, [')arallcl out shift if the clock frequency i~ 5 MHz? tA\ 0.2 (B) fi
'!i.

The tAl I B)

90.

The trnnslator programme t.bat converts ;ource ciJde mto machine corle line by Line io r.alled (A\ Assemb ler (B) Compi ler (C) Loader (D) Jot;.rpreter

91.

A 10 bit resistive divider is con,;ll·ucted. ~llcb that tbe rurreut tlU'oU~b the LSB resiM.or i:; 100 p A. The maximum curren~ thu~ will flow through the MSB r~:s•stor m

difference between PLA and RO~I ig PLA IS a combinattonalrlrruit, ROM 19 tt <equential circui ROM IS a combinarional ~trCult, PLA I" 11 ~equential circUit PLA econornises ou the number of m.in-tl:'rru~ (D) ROM economises on the memory

rnA is (A) 92.

0.2

(B)

(C)

1

.>1.2

lD)

102A

For a certain -1 bir successtvc appro:umation AID convener, the mn:umum ladder output is +8V. If a constant +6 V is applied to the anaput the sequence of binary states is (AJ 111l (B) 1010 (C) 0110 (D) tOll 11

138

93.

The initial state of MOD·l6 down converter is 0110. What state will it be after 37 clock pulses? (A) Indeterminate (13) OllO (C) 0101 (D) 0001

94.

A lOMHZ square wave clocks a 5 bit ripple counter. The frequency of the 3'~ FF's output in MHz is (A) 2 (B) 1.25 (C) 50 (D) 0,615

95.

In FF clocking (A) (B) (C) (D)

Hold time is greater than set up time Set up time is greater tha11 hold time Hold time is before edge triggering Set up time is after edge trigge ring

96.

J..mong the logic families, the family which can be used at very high frequencies greater than 100!\I!Hz in a 4 bit synchronous counter is (A) TTLAS (B) CMOS (C) ECL (D) TTLLS

97.

Among the following gates, the one to be operated under high noise condition is (A) ECL (B) Zener TL (C) FL (D) TTL

98.

In index addressing mode the eflective address is given by

99.

(A)

The index value

(B)

The sum of the index value and the operand

(C)

The operand

{D)

The diCference oC che index t·egister v«lue and the operand

For a 1-1 P syst~m using IO mapped IO the following statement is not true (A)

Memory space available is greater

(B)

Not all data transfer instructions are available

(C)

IO and memory spaces are distinct

(D)

IO address space is greater

100. PCHL is useful in 1mplementing

138

(A)

If then else construct

(B)

(C)

Case construct

(D) Call construct

12

,,

While construct

ENTRANCE EXAMINATION FOR ISSION, MAY 2012. Ph.D. (ELECTRONICS & COMMUNICATION ENGINEERING) COURSE CODE : 138 Registct• Number ·

, _ 1_ _ _ _ _ _ ,

Sig11aturP <>( th' /11 ui!(ilator (with dat')


Max : 400 Marks

!ru;tmctions to Candidates; 1.

Write your Number within the box provided on the top of this page and till in the page 1 of the answer sheet using pen.

2.

Do not write your name anywhere m this booklet or answer sheet. ViolAtion of this entails disqualification.

3.

Read each of the question carefully and shade the relevant answer (A) or (B) or
•1.


5.

Do not writP. anything in the question paper. Use the wrote sheets attached at the end l(lr rough works.

li.

Do not open the question paper until the start siJ
7.

Do not attempt lo answer after stop signal is given. Any such attempt will dh•quahfy your candidature.

8.

On stop sii!Jlal, keep the question paper and the answer sheet on your tAble and W!lit for the invigilator to collect them.

9.

URe of Calculators. Tables, etc. arc prohibited.

1.

Satellite tracking stations are located in remote areas in order to minimize the effect of (A) solar noise (B) manmade noise (C) cosmic noise (D) therma I noise

2.

24 hour satellite (synchronous satellite) should be placed in an equatorial orbit with a approximate height of (A)

1500 km

(B)

2000 km

(C)

5000 km

(D)

36000 km

3.

A satellite that simply reflects back the signals from one region of the earth other region is known as (A) orbiting satellite (B) geostationary satellite (C) active satellite (D) ive satellite

4.

A radio communication link is to be established vis the ionosphere. The virtual height at the midpoint of the path is 300 km and the critical frequency is 9 MHz. The maldmum usable frequency for the link between the stations of the distance 800 km assuming the flat earth is (A) 11.25 MHz (B) 12 MHz (C) 15 MHz (D) 25.5 MHz

5.

If a sky wave with a frequency of 50 MHz is incident on the D-region at an angle of 3o• then the angle of refraction is

(A)

15•

(B)

60•

(C)

30•

to

the

(D) 5.5•

6.

In a satellite ground station. the received signal is directly amplified in a low noise parametric amplifier foUowed by a FET amplifier. The gains and effective noise temperatures of the amplifiers are 20 dB, 9 K and 10 dB, 200 K respectively. The effective noise temperature of the combination is (A) 11 K (B) 20 K (C) 29 K (D) 39 K

7.

If a satellite is launched at an orbital radius of twice that of a geostationary satPilite, how much time will the launched satellite take to travel around the earth? (A) 48 hrs (B) 12 hrs (C) 96 hrs (D) 6 hrs

8.

Communication satellites are allotted bandwidth of 500MHz. This can be increased by using (A) Frequency and polarization reuse (B) (C) (D)

138

Time division multiplexing Frequency division multiplexing Triple modular redundancy

2

9.

The power transmitted by a synchronous orbit satellite antenna is 480 W. The antenna has a gain of 40 dB at 15 GHz. The earth station is located at distance of 24,567 km. If the antenna of earth station has a gain of 32 dB, the power 1•eceived is (A) 32 pW (B) 3.2 fW (C) 10.2 pW (D) 1.3 tW

10.

Antenna elevation angle al the ground station for satellite communication is always kept above 5° to (A) Minimize the sky noise temperature (B) Reduce the effect of oxygen and water vapour absorption on the antenna noise temperature (C) Minimize the sla nt range (D) Increase the visibility of the satellite

11.

The RST 5.5 inter1-upt service routine start from location (A) 0020H (B) 0024H (C) 0028H

(D)

002CH

12.

The instruction, that does not clear the accumulator of 8085, is (A) XRA A (B) ANI OOH (C) MVI A,OOH (D) None of the above

13.

An 808.') microprocessor based system d1-ives a multiplexed 5-digits 7-segment display. The digits at·e refreshed at a rate of 500Hz. The ON time for each digit is (A) 4 ms (B) 0.4 ms (C) 10 ms (D) 25 ms

14.

The content of Accumulator of 8085 microprocessor after execution of the following inRtructions will be 1YMA,A7H ORAA

RLC (AI

F'Fh

(B)

4Fh

(C)

3Fh

(D) CEh

15

A miemproccssor with 12-bit address bus will be to access ........ kilobytes of memory (A) 0 1 (B) 2 (C) 10 (D) 4

16.

Consider the following loop XRAA LXI B. 0007H LOOP: DCX B JNZ LOOP The lonp will be executed (A) 1 limes (B) 8 times

(C) 3

7 times

(D)

Inf'mi.te times

138

17.

18.

How many and what are the machine cycles needed for execution ofPLJSH B'! (A)

2 fetch and 1 memory write

(C)

3 fetch and l memory write and read (D)

3 fetch and 2 memory read

1

(B)

(C)

2

3

(Dl

4

A memory system of sire 26 K byres is required to be de8igned m;ing memory chips which have 12 addresses and 4 data lines each. 'fhe number of 8uch chips required to design the memory system is IAl

20.

3 fetch and 2 memory wl'lte

The total number of memory access involved (inclusive of the opcocle fetch) when an 8085 processor executes the instruction LDA 2003 is (A)

19.

(B)

2

(B)

4

(C)

8

(D)

16

Tbe number of memory cycles required to execute the following BOil.') in9tructions (i) LDA 3000H (ill LXl D, FOF 1 H would be (A) 2 for (i) and 2 for (ii) (B) 4 for (i) and 3 for (ii) (C)

3 for (i) and 3 for (ii)

(D)

3 for (i) and 4 lor (ii)

21.

For a Gunn diode oscillator, the drift velocity of the electron is 107 cm/s and the activt: region length is lOxlO-' em. The natural frequency of oscillation would be (A) 1 MHz (B) 10 MHz (C) 1 GHz (D) 10 GHz

22.

For a parabolic reflector antenna with diameter of 3 m. the far field pattern measurement at 10 GH:.: should be carr1ed out at a distance of a least (A)

30m

(B)

200m

(C)

400 m

(D) 600 m

23.

In a microwave measurement setup, the power reaching to the load is tound to be 50 mW. If a 3 dB coupler IS placed before the load, the power to tht- load will be (A) 50 mW (B) 25 roW (C) 1::!.5 mW (D) 6.25 mW

24.

For rectangular waveguide of dimensions: 1.732 ax a em. the cut off frequency for the TEw mude is 2 GHz. What is the cut off frequency forTMu modo: m the wavegmde? (A) l GH~ (B) 3.46 Gl:lz (C) 4 GHz (D) 6 GHz

25.

Two microwave signals tr&velling 111 the space have a path length dilference of 3 em when operating at 10 GHz. What is the relative phase difference of the signal~'?

138

2n

(B)

n

(C)

4

3n

(Dl

4n

26.

ln mensurin!! pulsed microwave power. the pulse duration is 1.5 IJS with PRF of I kHz. If the CW power sensor reads 15 mW, what i: rel="nofollow"> the average signal power during the pulse CAl

27.

25 GHz

(B)

20 GHz

(C)

3.5

(B)

5.5

!l.6 GHz

(BJ

6.789 GH;~

tr the peRk power of a pulsed microwave !<00 W. lhcn the duty cycle will be tAl

:H

(CJ

80%

(B)

8%

(C)

A dipole amenna of iJ8 length <'ffil'll:'ncy of the antenna is

(OJ

125 GHz

6.25

(Dl

7

5.543 GHz

(CJ

(D) :3,92 Gllz

is 10' Wand the averngc J>OWL•r

0.8'!-n

(D)

~~

0.011': ..

O.f-19 159%

(B)

ha~

8.9159%

2.4456•

a.441it3

an equivalent total loss resistance of I .'> U, Tht• (C)

89.159%

(D) 891 ,)9" ..

A tru nijmittang antenna has a gain of l 0. H is fed with a 1ngnnl powt•r of 1 W A~~uming free space propagation, what power would be captured by u n•co:1vm~ untl•nnu of effective at·ea 1 m~ in the borl' si!(ht direction at a distance of 1 m't 1Al

:-14

(D) 20 W

An antenllfl hal' a gam of 44 dB. Assunung that the main beam of the antt>nnu i, cunalnr m cros:s section. the beam width wall be

(t\l

:33.

12.5 GHz

~

(C) :1~.

15 \\'

A cylindrical cavity operating in TEua mode has a 3 dB bandwidth of 2.·1 MHz and ib quahty factor is 4000. Its re,;onant frequenc) would be

tAl :30.

10 W

On n micro strip line. the wavelength measures are 12 mm for a 10 Gllz .;ignnl. The dwlectrac constant of the equwalent homogeneous line is

~9.

(B)

An IMPAT'I' diode has a drift length of 4J.Im. The drift velocity of Si islU'•m/s. The operating ft·cqucncy of IMPATT diode iij

tAl 2!<.

5W

10 W

(B)

1W

2W

(Dl

0.~

w

,\n caa1h ,tataon employs a I k\V hi~h powl'r amplifier (HPAJ and a :W m Ca-s gram antenna whose transmitted j!ain t::< 6-~ dB at a fret> space wa,·pJength of :!.1 em. If the loss of th1• "avt:length that t'ODDl'CtS HPA to the feed is 1 dB, than the c:u·th stataon EIHI' is .

29 dBm

59 dBm

tC)

94 dBm

(D)

12~

dBm

138

:lfi.

Two identicaluniennas 1 km apart and operating ut 1.=10 em in an LOS link, huve nn obstacle lOrn high midway bet.woon them. '!'he height. of the ant~nnas such that tlw fist Fresnel zone is free of any obstacle. should be (A) 15m (13) 18 111
36.

A parabolic dish 11nlenna has a daumet.er of 1 m. The max1mum possable (ideal) gam of the antenna at a wavelength of !3.14 em is (A) 20 dB (B) 30 dB (C) 40 dB (D) 50 dB

37.

A transm1ttmg antenna with a 300 MHz earner frequency produced 2 kW of power. lf both antennas has unity power gain, the power r(. rel="nofollow">eeived by anoth<:r antenna at n chstance of 1 km is (A) 11.8 mW (B) 18.4 W (C) \1:!.4 fl. W (D) 12.7fl.W

at~ .

A thm dipole antenna is Ml5 long. If its loss t·eststance is 1.2 n. tht> l.'fliciency is (A)

3!1.

59%

74.5%

(C)

1.974 n

(B)

1.263 n

2.Hl6 n

i~

2.693 n

For a Hertz dipole antenna, the half power beam width (HPBW) in the E·}llane is (A)

4l.

(B)

An antenna can be modelled us an electric dipole of length 4 m at :ll\llh.. 11 current uniform over its length, then radiation resistance of the antenna is

40.

.U.l ~

360•

(B)

180•

(C)

9(1>

(!))

45•

An ideal pulse radar receiver

(Cl

should have very large bandwidth should have very small bandw1dth both (A) and (B)

none of these

(A) (B)

42.

In case the ratio of the antenna diameter to the wavelength in a radnr systttm is high, this likely not to result in
·1:3.

Radar detection •s limited to hne of stght beeuu6e

tC)

of curvature of the earth the wavus are not reflected by the ionosphere long wavelengths are U~t!d

CD)

short wavelengths are used

(A)

CB)

138

6

44.

In a radar system, if the peak transmitted power is increased by a factor of 16 and the antenna diame1 er is power is increased by a factor of 2, then the maximum range will increase by a factor of (A)

45.

46.

16

(B)

(C) 4

8

(D)

2.828

A received signal in a radar system occupies an IF bandwidth of 12 MHz. If the transmitted signal was a pulsed carrier of 10 GHz with duty ratio 1:0.5@ 400 Hz. the received signal power will contain the (A)

Frequency component at 400Hz

(B)

Frequency spread over the whole IF bandwidth

(C)

De or average value of the IF

(D)

RF signals at 10 GHz and 12 MHz

If the average power of radar transmitter is 2 kW and the peak power of the transmitter is 1000 kW, what will be the duty cycle?

0 002

(B)

0.02

(C)

0.001

(D) 0 .01

.J7

Radar receives an echo from a target 20J.1s after sending the signal. The approximate range of the target is (C) 600 m (D) 6000 m (A) 300m (B) 3000 m

48.

In precipitation mode, how often are NWS radar images updates: (B) every 50 seconds (A) every 5 seconds (C)

49.

50.

every minute

(D)

every 5 minutes

Radar beacons are used for (A} Target identification (B)

Navigation

(C)

Causing significant extensions of the maximum range

(D)

All the above

In a radar in case the return echo arrives after the allowed pulse interval, then

It will not be received

(ll)

The receiver will get overloaded

It may interface with the operation of the transmitter

(D) The target will appear closer than it. really is 7

138

51.

52.

If a common emitter amplifier with an emitter resistance Re has an overall 'l'rans conductance gain of -1 mAIV, a voltage gain of -4 and desensitivity of 50, thE rel="nofollow">n the value of the emitter resistance Re would be (A)

50 kn

(B)

o.98 kn

(Cl

•'iO Mn

(D)

0.98Mn

The voltage gain of an amplifier without and with negatiV<" respectively is 100 and 20. The percentage of negative (f3) would be (A)

53.

54.

(B)

5%

(C)

20%

(D)

80%

An amplifier using BJT has two identical stages each having a lower cut-off(:-! dB) frequency of 64 Hz due to coupling capacitor. The emitter by capacitor al;;o provides a lower cut-off (3 dB) frequency due to emitter degeneration alone of 64 llz. The lower (3 dB) frequency of the overall amplifier is nearly (A)

100Hz

(B)

128Hz

(C)

156Hz

(D)

244Hz

The input voltage of zenet· regulator varies from 20 V to 30 V. The load current \'arJes from 10 mA to 15 rnA. If the zener voltage is 5 V, the valu e of series resistor will be (A)

5.5.

4%

1 kn

(B)

1.5 kn

(C)

1.66 MO

(D)

2.5 Mn

A de-de converter has an efficiency of 80% and is supplying a load of 24 W at 240 V _

What is the currcnL drawn from the battery if the converter is working from a baLtcry of 12 V? (A)

56.

57.

138

0.1 A

(B)

2.0 A

(C)

2.5 A

(D)

10 A

What is the value of R, required to self bias an N channel JFET with V,, Tos"= 40 m.A and VGsQ= -5 V? (A)

250 Q

(B)

5000

(C)

750 n

(D)

1500 n

= - 10 V.

A half wave rectifier having a resistance load of 1 kn rectifiers an A.C voltage of 325 V peak value and the diode has a forward resistance of 100 n. What is the RMS value of the cul'!'enl? (A)

295.4 mA

(B)

94 m.A

(C)

147.7 rnA

(D)

208 mA

8

58.

A zener diode in the circuit shown in the figure is has a knee current of 5 rnA, and a maximum allowed power dissipation of 300 mW. What are the minimum and maximum load currents that can be drawn safely from the circuit, keeping the output voltage''" constant at 6 V?

(A) (C)

59.

(B) (D)

5 mA, llO mA 60 mA, 180 rnA

The maximum power that can be transferred to the load resistor Rdrom tht> source m the figure is

(A)

60.

0 rnA, 180 rnA 10 rnA. .55 mA

1W

(B)

10 W

(C)

0.25 W

{D)

volto!(~·

0.5 W

The circuit. using a BJT with f3 = 50 and VaE=0.7 Vis shown in the figure. The base ct1rrent To and collector voltage Vc are respectively ~QV

V.

(A)

43 f.IA and 11.4 V

(C)

45 !tA and J 1 V

(B) (D)

9

40 J.IA and 16 V

50

~A

and 10 V

138

61.

For a single mode optical cable v.ith 0.25 dBikm lo,;s. the optical powl'l" I 00 km from a 0.1 mW source will be (A)

62.

(B)

316.22 ~·W

(C)

o.:H6 mW

(D)

:)1.6 mW

A GaAs optical source w1th a refractive index of 3.6 is coupled to a silica fihre that ha8 a refractive index of 1.48. If the fibre end and source are in clObC phyt:ical rontact. then the Fresnel reflection at the interf'acl' 1~ (Al

63

:H.6 )lW

(B)

2.3

1.9

(CJ

tDl 0.17-t

1.!\

A glass fibre has rP.fl'llctive indices n, of 1..5 t!nd n2 of l. Assuming<'- :1 x I 0" m/s the

multipath time dispersion will be

tAl 6-1

0.8575

(B)

0.9260

(CJ

0.3500

(0)

0.1 :i!'!H5

0.832 AW

1

0.714AW·

(C)

0.694 AW

I

(0)

0.452 AW

I

The normalized frequency of a step index tihrc lb 28 and 1300 nm waveltmgth. What is the total number (approximately) of guided modes that can be ~upported by thofibre? (A)

Gi.

n ns/m

2.55 11s!m

What is the respons1tivily of the photodiodt> having quantum efficiency of 6,1% with photoru; of energy 1.5x 1()- 1"J mcident upon it'> (AI

66.

(B)

A certain optical fibre has refractive index of clad (n,l=l.4 and that of core (nz)=l.05. 1t~ numerical aperture will be (t\)

65.

2.5 nslm

50

{B)

200

{C)

400

(D) nOO

For a ::'\1:\.IS fibre n,=1.5und nt=l.46, than thl• cnllcal angle and acr!!plRnce

angl~>

will

he

6b.

(A)

20.12• and i6. 73 1

IBl

76.73° and 20.12•

(C)

29.12" and 78. 73'

(0)

78.73° and 29.12 '

Photons of energy 1.53 >< 10 •9 J are inc1dent on a photo diud~ whJCh has a r~:sponSIVlt)' of 0.65 AJVo.'. lf the optical power ltovcJ is 10 rW. then the gencrutPd photo current is (AI

138

2.3 J.tA

(8)

6.5 ItA

(C)

10

6 .:1 I'A

(D)

6.1

jl •.\

69.

A single mode optical fibre has a beat length of 8 em at 1300 nm, then the birefringence will be

70.

X

1~

(B)

1.89 X 10'

(C)

6.55

X

10 •

(D)

1.63

X

10"'

A double hetro junction TnGaAsP LED emitting at a peak wavelength of 1310 nm has radiative and non· radiative recombination times of 30 and 100 ns, respectively. The drive current is 40 rnA then the bulk recombination life time will be (A)

71.

3.61

231 ns

(B)

23.1 ns

(C)

2.31 ns

(D)

0.231 ns

What is the nyquist rate for the signal x(t) = cos2000rrt+3sin6000nt?

2kHz

(B)

-1 kHz

(C)

12 kHb

{D)

6kHz

Which one of the following is corre<'t? Energy of a power signal is

73.

(A)

finite

(Bl

0

(C)

infinite

(D)

between 1 and 2

A system has poles at 0.01 Hz, 1 Hz and 80 Hb; zeroes at 5 Hz. 100 Hz and 200 Hz. The approximate phase of the system response at 20Hz is (A)

74.

go•

0 Hz

(B)

0.75 kHz

(C)

0.5 kHz

{D) 0.25 kHz

What is the period of the sinusoidal signal x(n)=5cos[0.2nn]'? (AI

76.

o•

A 1 kHz sinusoidal signal is ideally sa mpled at 1500 samples/sec and the sampled signal is ed through an ideal low· filter with cut·off frequency 800 Hz. The output signal hns the frequency (A)

71'>.

-9Qo

10

(B)

5

(C)

1

(D)

0

Consider the following statements
(i), (ii), (iii)

(B)

(ii). (iii), (iv)

(i), Ciiil, Civl

(D)

All

11

138

77.

7H.

The sinusoidal s1gnal has fundamental period N=lO samples. The smallest ongular frequency. for which x(n) is periodic, is (A)

1110 radlcyclc

(B)

10 radlcycle

(C)

.'i rad/cyrlt>

(D)

n/5 radlcyrle

If a fund ion f(LJ u(t) is shifted to right sidP by to, then the functwn can be expreBsed as,

79.

~A)

f(t- tu) u(t)

(B)

f(t)

(Cl

f

(D)

f(t+ lro) u(l + tu)

The avprage value of tlw full wave rt•ctified sine wave with pPriod n, and pPak vnluP

~0.

81.

tt rel="nofollow">) u(l· to)

u
0.707\lm

(C)

0.500 Vm

0.637 Vm

(D)

0.318\1".

Two rectangular waveforms of duration T, and Tz sPcond an• convolved. What is thl" sha pt• of the resulting waveform? (A)

Triangular

(R)

RPctangular

(C)

Trapezoidal

(D)

Senn·<'ircular

A typical number of diffusions used in making epitaxial diffused silicon integrllled circuit is (A)

!l~ .

ll4.

:'l

(D)

4

50 nm

{B)

14~ nm

(C)

350 nm

(D)

1 ~·m

Tlw maximum cl .. pletton laver width in silicon ,,.. (Al

0.11~

1 1-101

11m

{B)

0.857 ~tm

(D)

1.1-13 ~tm

Tht> suurcf' of a silicon (n,=10 10/cm'' )n·channel :\lOS transistor has an Area of 1 sq 1-1111 and a depth of 1 lim. lf the r!opant density in thP soured is 10 19/cmJ, the number of holes in the som·ce region with the above volume is approximately

tAl

138

(Cl

2

The gate oxirle thicknes~ in the ~108 capacitor is (AJ

R:l.

(B)

1

101

(B)

(CJ

100

12

10

(D)

0

155

In •he .'\!II OS mverlt'r

(,\) tC')

l 111

Both dt1ver and lmulllt'P dPpiPtJOn l vp<•

,\ dt'p!.•uon type 1\'MOS 1,. "l"'l'>'llt·
tAl :-.7.

h~:HJ

an• enhann·m<·nt t.\'Jl" Tlw driver and 1~ o)ll h:lll<'<'llleM typl' and Jon d t!Ptiletton I y I'" The drive i~ <·tion h'PP .ltld loar.lt•nhnn<'<'llWilt tvpc

(ll)

li6.

Tlw drl\er and uctl\1!

1

v

l~ketrtnt

(C)

1 V. h1r "•·• ~:; V a<.

IV

(ll)

mnhihry and hfr· time m n s<'ntH'ntHluctor at O.!ll1 tn;IIV•l JliHI 'l·lO f'K Th.., rli('(ll Si~> tl lt·nvth ;,

1'<'01'1

7\'

l<•tnp<'ralut·P tll'e

rr·~w·etivPly

IAJ

1'1'

3.1!! nm

{Dl

I 77 nm

(!')

t\n mt rtn.~tc ~E'tnt-conductor wtth enerc:y gap 1 "V hn~ n can;,.r conc.,nl muon '.: &t tcmpl'ntture :.!0() K. J\nnthl!r intnndc SPmi-conclur.tw· ha>' thP ~nnw vnlu•• of rnrnH ronccntrat1nn 1' at lt"nl(lt'rnltlrte t'>OO K. Wh11l •~ thr> ••n1-rgy gap vahtt• lor tlw sPCond .•wJnlC'ondttr.'to r·l ((')

!oo!l

l!O.

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:l

,.y

ISf''~tion di!Tu~ton" Ill II tnono!tthtc rc t"rE'Ulf'S I'Olll'l'111t"lltJOn of n·gton between the tsolntion tsbnd,.; of thl' on!cr nf (Al lOt:cm 1111 )()20.-m ' ((') 10-'cm 1 The L'hemicH! J'l'U<"tlllll mvolved in epttnxtal gmwth in tt-mp••rn 1ure of :tho ttl. (Ill

''I

J ;l.l!l ntn

,1,5!) nm

iHIO'f'

l'ht numb..r of lm• n!•tliB'•''' to tAl 113:! hib (C)

I '-'96 bit-

(J\1

Otol

til!

(CI

~tore

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COl

IC ehtps

\200'('

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lflk•·~

(Dl

the

plact• at a

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2">fi HIIH\!t' with :;2 grH) IPv••l;;

IIH

327!ih(l b1ts

(Ill

J51l71Jll~

0 to 15

l'lu· etft·l'l. t·au,t•tl bv thl' U~• <>f <1n uf .1 d;Jlilnl i•JUll!< 111 <'nlit·tl

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ntttn
v\ I

Inbe cr.:.tntcrmg

({.')

tnt J>laolP

(!))

13

tJI ~month

area"

tlotnmn~;

138

94.

9fi.

Sampling of an imng<>

tx~quircd

for

(A)

quantization

(RJ

ijhRJ'Pening

(C)

smoothing

(fJ)

digitization

An Image function f(x.yl (A)

1~<

characterized by f(x,yl= i(x,y) r(x,y) wh£m•

0 < i(x,y) < 1 & 0 < r(x.yl <

x>

(R) 0 < t(x.y) < 1 & 0 < r(x.yl < 1 (C') 0 < i(x,y) <"' & 0 < r(x,v) < :c

(D) 0 < i(x,y) < •:o & 0 < t•(x,yl < 1

96.

Consider an imag<' of siz(' M x N with (i4 grny levels. The total number of bits l'('qutred to store l hiH dil!it izes image is (A)

97.

:\1 "

~ X

64

(B)

i:\! " N

X 6:~

(C)

~ X

,\[ "

6

(D) :\-1

~

N

X

8

A pixel P 11t coordinnlc8 (x,y) has four hortzontal and verticAl m•tghhnur:; whose coordma tes are givC'n by (A)

(x-1, y-1), (x l,y) , (x,y-1). (x,y+1)

(x+1, y), (x· 1,y), (x,y+J), (x,y-1)

(x+1. y-ll, (x+ l.y). (x.y+ 1). (A·l.y+l)

An image of sizE' 1024 quantity (A}

9!J.

require~;

1 KB

x 1024 pixels in which tlw intensity of £>~~ch pi.xt>l

2 unit

(Bl

((')

1MB ~ystem

2 KB

distnnr£• h1•t wt·cn centre pix<'I and rorm'r pi.xcl is

1 unit

!L'l

1Oil. The 08 distance (chess l'loard distance) between ill ucfined as

138

An S-hit

the storage space (if not compretiscd)

In R-di5tance mensuremomt (Al

11:1

1..)

r

umt

(0)

and q with COOl'dtnnll.•6 (x, y), (s. t)

(A)

(x-s)+{y-t)

(13)

max (I x-s I . I y-tl)

(C)

[(x-s)+(y-0)2

(!))

mm

14

1.75 umt

y-t

I>

ENTRANCE EXAMINATION FOR ISSION, MAY 2013. Ph.D. (ELECTRONICS AND COMMUNICATION ENGINEERING)

COURSE CODE : 138 Number :

Signature of the Inuigilator (with date)


Max : 400 Marks



2.


3.

Read each of the question carefully and shade the relevant answer (A) or (B) or (C) or (D) in the relevant box of the ANSWER SHEET using HB pencil.

4.


5.

Do not write anything in the question paper. Use the white sheets attached at the end for rough woJ;ks.

6.


7.


8.


9.


1.

Spectral efficiency of QPSK null to null having bandwidth 4Hz, will be (A)

2.

3.

1/2

(B)

(C)

114

3/4

(D) 1

What is the bit error of a non-coherent FSK system modulated by a PCM signal bit stream and operating at 10MHz? Frequency deviation is 850Hz, system data rate is 100 bits/sec, peak to peak carrier amplitude is 2 volts and double noise spectral density is 1 x 1Q-4 volts/Hz. (A)

2.74

X

(C)

3.74

X

10-6 lQ-6

(B)

4. 74

X

10-6

(D)

5.74

X

10-"

Frequency Shift Keying is mostly used in (A)

radio transmission

(B)

telegraphy

(C)

telephony

(D)

none of these

4.

What is the average probability of error in a coherent FSK (1 bit decoding) system transmitting binary data at 2.5 x 106. bits/sec, while Gaussian noise of zero mean and spectral density 10-20 volts/Hz added and with no noise, amplitude of required signal is 111v. (A) 0.55 X 10-3 (B) 0. 75 X 10-3 (C) 0.65 X 10-3 (D) 0.85 X 10-3

5.

The bit rate of a digital communication system is 34 Mbits/sec. The modulation scheme is QPSK. The baud rate of the system is (A)

6.

138

(C)

17 Mbits/sec

(D) 8.5 Mbits/sec

BPSK

(B)

QPSK

(C)

QAM

(D) MSK

10 bps

(B)

12 bps

(C)

11 bps

(D) 13 bps

If binary PSK modulation is used for transmission, the required minimum bandwidth is 9600 Hz. To reduce transmission bandwidth to 2400 Hz, the modulation scheme to be adopted should be (A)

9.

34 Mbits/sec

Transmitted power ST = 200mW, L = 90 dB, n =1Q- 15 W/Hz and Pe = 10-4 The maximum allowable bit rate using non-coherent FSK, will be (A)

8.

(B)

If a carrier modulated by a digital bit stream had one of the possible phases of 0, 90, 180, and 270 degrees, then modulation is called (A)

7.

68 Mbits/sec

QPSK

(B)

MSK

(C)

16-ary QAM

Which of the following is not correct for DS-SS.? (A)

Modulation technique used is BPSK coherent

(B)

Variable chip rate

(C)

Long acquisition time is required

(D)

Effect of distance is high

2

(D) 8-ary PSK

10.

The chip rate for slow hopping FH-SS is given by

(A) (C) 11.

12.

13.

14.

(D)

R

= Rh = T,

good power efficiency

(B)

constant envelope

(C)

uses non-linear amplifiers

(D)

requires small bandwidth

Temporal diversity can be realized by the following. (A)

Repetition coding

(B)

Automatic repeat request

(C)

Combination of interleaving and coding

(D)

All the above

Macro diversity techniques are used to combat (A)

Small scale fading

(B)

Large scale fading

(C)

Small and large scale fading

(D)

None of the above

Intersymbol Interference could be overcome by which of the following technique. Equalization technique Channel coding

(B)

Diversity technique

(D)

None of the above

Which of the following causes fast fading? (A)

Slow variation in the signal strength

(B)

Mobile station moves slowly

(C)

Large reflectors and diffracting objects along the transmission paths are distant from the terminal

(D)

terminal moves for short distances

In a block encoder, if k information bits are encoded into n code bits. The code rate is given by (A)

17.

&

(A)

(C)

16.

(B)

The linear modulation technique is characterized by

(A)

15.

= R, R, = 1/T, R,

kin

(B)

(C) n.k

n/k

(D) n+k

The received power at a receiver depends on (A)

Average bit energy

(B)

Transmission bit ra.te

(C)

Both (A) and (B)

(D)

None of the above

3

138

18.

19.

What is the purpose of Random Access Channel(RACH) in wireless communication? (A)

To transmit the payload data

(B)

To transmit the signalling information that is necessary during a connection

(C)

To request for incoming connection from the subscriber

(D)

To transmit and receive bursts appropriately

GSM system uses carrier frequencies around 10 MHz

(A)

20.

21.

(B)

(C)

90 MHz

900 MHz

(D) 9000MHz

Which of the following statement is not correct regarding CDMA? (A)

Many s of a system share the same frequency

(B)

The code sequence must be orthogonal

(C)

The powers of all signals arriving at the BS should be different

(D)

CDMA requires accurate power control

Frequency diversity is achieved by (A) , Transmitting signals through two orthogonally polarized propagation path

22.

(B)

Transmitting signals from several transmitter antenna

(C)

Enhancing the signals for closely spaced antennas

(D)

Transmitting information on more than one or more carrier frequencies

In (A)

23.

25.

138

'

4 QPSK, the maxim urn phase is limited to ± 45°

(B)

± 90°

(C)

± 135°

(D) ± 180°

The resulting change in frequency due to Doppler shift is given by (A)

24.

tr I

fo

= f, - f,

(B)

fu

= f, - f,

(C)

fo

= f, + ft

(D) fo

= f,

x f,

Which of the following is the merit of Okumara's model? (A)

Accuracy in parameter prediction

(B)

Suitable for modern land mobile radio system

(C)

Urban and Suburban areas are analysed

(D)

All the above

The factors influencing small scale fading is (A)

MUttipath propagation

(B)

Speed of the mobile

(C)

Transmission bandwidth of the signal

(D)

All the above

4

·----~------------------------------------------------------

26.

27.

28.

29.

Numerical aperture is used to obtain (A)

Angle of incidence

(B)

Acceptance angle

(C)

Refractive indexes

(D)

Relation between acceptance angle and refractive indexes of core

The path followed by skew rays through the fiber is (A)

Parabolic path

(B)

Spherical path

(C)

Helical path

(D)

Circular path

The mode value for a step index fiber is related to the normalized frequency as (A)

M, = 0.5V,

(C)

Ms

31.

M, = 0.25V,

(D)

M,

= 4V,

Rayleigh scattering produces an attenuation proportional to (A)

30.

= 2V,

(B)

1

1/-1.

(B)

3

(D) 1/ ,1.;'

(C) -1.

/l."

Group Velocity Dispersion arises due to (A)

Variation of the refractive index of the core material as a function of wavelength

(B)

Finite spectral emission width of an optical source

(C)

20% of light propagating in the cladding travels faster than the light confined to the core

(D)

All the above

Intermodal dispersion can be minimized with the use of (A)

Monomode step index fiber

(B)

Multimode step index fiber

(C)

Multimode graded index fiber

(D)

All the above

32.

Given core refractive index is 1.5 and cladding refractive index 1.47. The Numerical Aperture of the fiber is (D) 0.40 (C) 0.35 (B) 0.30 (A) 0.25

33.

A graded index fiber has a core with a parabolic refractive index profile which has a diameter of 50 )1m. The fiber has a Numerical Aperture of 0.2. What is the normalized frequency when it is operating at a wavelength of 1)1m. (A)

21.4

(B)

(C)

31.4

5

41.4

(D)

51.4

138

34.

Two polarization maintaining fibers operating at a wavelength of 1.3!lm have beat length of 0.7mm. The modal birefringence is (A)

35.

37.

38.

40.

138

10 60

(B)

1.86

X

103

(C)

1.86

X

10-3

(D) 1.86

X

10-6

0.8l11m

(B)

l.8l11m

(C)

0.08l11m

(D) 8.l11m

Solitons are pulses that travel along the fiber (A)

Without change in shape and with change in amplitude

(B)

With change in shape and without change in amplitude

(C)

Without change in shape and amplitude

(D)

None of the above

The intrachannel crosstalk arises due to (A)

interfering signal is at the same wavelength as the desired signal

(B)

interfering signal comes from a neighbouring channel that operates at a different wavelength

(C)

Both due to (A) and (B)

(D)

None of the above.

The error rates for optical fiber telecommunication systems ranges from (A)

39.

X

A photodiode is constructed at GaAs, which has a band-gap of 1.53eV at 300°K. The cut-off wavelength is given by (A)

36.

1. 86

10-3 to 10-"

(B)

10-" to 10-9

(C)

10-9 to 10-12

(D) lQ-12 to 10-1s

Intersymbol Interference occurs due to (A)

discrete nature of current flow in the device

(B)

pulse spreading in the optical fiber

(C)

detector load resistor and amplifier

(D)

none of the above

Find the technique used for determination of fiber numerical aperture. (A)

farfield angle from fiber using a scanning photodetector and a rotating stage

(B)

farfield pattern by trigonometric fiber

(C)

farfield pattern of NA measurement using a rotating stage

(D)

all the above

6

41.

42.

43.

The bulk dark current noise is due to (A)

thermally generated electrons and holes in the pn junction of the photodiode

(B)

surface defects, bias voltage and surface area

(C)

statistical nature of the production and collection of photo-electrons, when an optical signal is incident on a photodetector

(D)

bias circuit when no light is incident on the diode

The response time of a photodiode depends on (A)

Transit time of photo carriers within the depletion region

(B)

Diffusion time of photo carriers outside the depletion region

(C)

RC time constant of the photodiode and its associated ciruit

(D)

All the above

The radiative and non-radiative recombination hfe times of the minority carriers in the active region of a double heterojunction LED are 60 ns and 100 ns respectively. Determine the total carrier recombination lifetime. (A)

44.

46.

(C)

37.5 ns

47.5ns

(D) 17.5 ns

46

(B)

(C)

48

50

(D) 52

Which of the following is not the characteristic of LED? (A)

Optical output is coherent

(B)

No optical resonant cavity

(C)

Output radiation has broad spectral width

(D)

No spatial and temporal coherence

The process of ing two fibers is called as (A)

4 7.

(B)

An avalanche photodiode produces a multiplied photocurrent of 1211A. Calculate the multiplication factor if the primary photo current is 0.25~!A. (A)

45.

27.5 ns

Connecting

(B)

(C)

Splicing

Coupling

(D) Filtering

Microscopic bending losses can be minimized by (A)

Introducing compressible jacket over the fiber

(B)

Deg fibers with large relative refractive index difference

(C)

Operating at the shortest wavelength possible

(D)

None of the above

7

138

48.

The total rms pulse broadening is given by the expression (A) (C)

49.

50.

Insertion loss in FBT structure is defined as (A)

Ratio of power input to power output

(B)

Ratio of back scattered power received at the second input port to the input power

(C)

Loss obtained for a particular port to port optical path

(D)

None of the above

If there are 10 output ports, calculate the splitting loss that occurs in star coupler. (A)

51.

52.

53.

54.

55.

138

5

(B)

10

(C)

15

(D) 20

An exponential signal represented by x(t) = e", in which if a= 0 then the signal x(t) is (A) DC signal (B)

Sinusoidal signal

(C)

Exponentially decaying sinusoid

(D)

Exponentially increasing sinusoid

Find the result of the following summation I~J5(n -2) cos 2n +5(n -1) sin 2n] (A)

Cos 4 + Sin 2

(B)

Cos 2 + Sin 4

(C)

Cos 2 + Sin 2

(D)

Cos 4. Sin 2

A filter that has a constant magnitude response for all frequencies is known as (A)

Comb filter

(C)

All filter

(B)

Band filter

· (D)

Low filter

Aliasing can be prevented if the highest frequency component nm in the signal is (A)

Greater than or equal to T I 1r

(B)

Greater than or equal to 1riT

(C)

Less than or equal to T I 1r

(D)

Less than or equal to 1r IT

The Fourier transform of the sequence x(n) =1; for -2 S n S 2 (A)

1 + sin

(C)

1 + Cos

OJ OJ

+ sin 2 OJ

(B)

1 + 2Cos

+ Cos 2 OJ

(D)

1 +Cos 20J + 2Cos 40J

8

OJ

+ 2Cos 2 OJ

56.

57.

58.

Which realization is less sensitive to the process of quantization? (A)

Cascade form

(B)

Parallel form

(C)

Transversal form

(D)

Lattice form

(C)

Circle

FIR filters are (A)

Stable and do not have linear phase

(B)

Unstable and do not have linear phase

(C)

Stable and have linear phase

(D)

Unstable and have linear phase

The poles of the Chebyshev filter lie on (A)

59.

61.

62.

(B)

Parabola

(D)

Rectangle

The number of multiplications needed in the calculation of 1024 point FFT are (A)

60.

Ellipse

4608

(B)

(C)

10240

5632

(D)

5120

A low filter circuit is basically (A)

a differentiating circuit with low time constant

(B)

a differentiating circuit with large time constant

(C)

a integrating circuit with low time constant

(D)

a integrating circuit with large time constant

Which of the following represent a stable system? (A)

Impulse response of the system decreases exponentially

(B)

Area within the impulse response is finite

(C)

Eigen value of the system are positive and real

(D)

Roots of the characteristic equation of the system are real and negative

The Z-Transform of an anti-causal system is X(Z)

=

12- 21Z 3-7Z+12Z2

. The value of x(O]

IS

(A)

63.

-7/4

(B)

0

(C)

4

(D) None of these

Double integration of a unit step function would lead to (A)

an impulse

(B)

a parabola

(C)

9

a ramp

(D) a doublet

138

64.

65.

66.

67.

69.

70.

138

2

z -z-0.25

. The system is

(A)

Causal and stable

(B)

Causal, stable and minimum phase

(C)

Minimum phase

(D)

None of these

The impulse response h(n) for a realizable filter is (A)

Zero for n :S 0

(B)

Zero for n 2: 0

(C)

One for n :S 0

(D)

One for n 2: 0

The Butterworth filter is characterized by (A)

The number of poles are less when compared to the Chebyshev filter

(B)

Transition band is less when compared to the Chebyshev filter

(C)

The magnitude response decreases monotonically as the frequency from 0 to oo

(D)

The order of the filter is more when compared to the Chebyshev filter

n

increases

. H(.;m ) = -1The f requency response o f a causa I an d sta bl e LTI system 1s - .jm - . The 1+;m group delay of the system is (A)

68.

Z(3z-2)

The transfer function of a system is given by H(z)

2

1 + {t)2

(B)

-2 1 + {t)2

(C)

2 tan_, m

Errors due to round off noise are less severe in (A)

IIR filter

(B)

FIR filter

(C)

Butterworth filter

(D)

Chebyshev filter

The condition for impulse response to be symmetry is (A)

h(n)

= h(N-1-n)

(B)

(C)

h(n)

= h(n-1-N)

(D)

= -h(N-1-n) h(n) = -h(n-1-N)

h(n)

Which of the following is the desirable characteristic of the windows? (A)

The central lobe of the frequency response of the window should contain most of the energy and should be narrow

(B)

The highest side lobe level of the frequency response should be small

(C)

The side lobes of the frequency response should decrease in energy rapidly as m tends to tr

(D)

All the above

10

71.

The frequency response of N-point rectangular window is given by . (uN

(A)

WR(ejw)~

sm-.

(B)

2 {))

Slll-

2

(C)

WR(e;w )~

wN cos-.

2 {))

Sln-

2

72.

The main lobe width of Hamming window is equal to (A)

73.

74.

4;r N

Fixed point arithmetic

(B)

Floating point arithmetic

(C)

Block floating arithmetic

(D)

Both fixed point and floating point arithmetic

Ifb

(D) 1 :

= 3 bits, then quantization step size is 0.25

(B) 0.5

(C)

0.125

(D) 0. 75

The input - output relation of a factor:of-2 upsampler in the frequency domain is given by

(C)

Y(ejw) =X (e'j"') Y(e 1w) =X(ej 0 5 "')

(B) (D)

Y(ejw) =2X (ejw) Y(ejw) =2X(ejosw)

The perceptual attribute of colour is given by (A)

77.

(C)

(A)

(A)

76.

2

(B)

Overflow does not arise in

(A)

75.

2;r

Brightness

(B) Hue

(C)

Saturation

(D) All the above

Which of the following statement is not correct? (A)

Entropy is defined as the average information generated by the source

(B)

The maximum entropy is 8 bit, which occurs when both the messages are equally likely

(C)

The entropy of a source gives the lower bound on the number of bits required to encode its output

(D)

For a digital image considered as a source of independent pixels, its entropy can be estimated from its histogram 11

138

78.

79.

80.

81.

82.

83.

Light received from an object depends on (A)

Reflectivity of the object

(B)

Incident energy distribution

(C)

Both (A) and (B)

(D)

None of the above

Which of the following is not the property of Cosine transform? (A)

Real, symmetric and orthogonal

(B)

It is not the real part of the unitary DFT

(C)

It is a fast transform

(D)

It has excellent energy compaction for highly correlated data

Which of the following representation?

138

not

require

multiplication for

Haar transform

(B)

Hadamard transform

(C)

Sine transform

(D)

SVD transform

its

Haar transforms are useful (A)

for highly correlated data

(B)

for small block sizes

(C)

if higher spatial frequencies are to be emphasized

(D)

if use of frequency domain is mandatory

Image restoration is concerned with (A)

removal or minimization of known degradations in an image

(B)

making quantitative measurements from an image

(C)

accentuate certain image features for subsequent analysis or for image display

(D)

characterization of the quantity that each pixel represents

According to root law, contrast and luminance are related as c = fh

(B)

c

= f1tn

(C)

C

=

Unfl/n

(D) c = 50 log10 f

If a mixture of colour C! and C2 matches a mixture of colour c1' and c2, then according to colour subtraction which of the following is correct if [c2] = [c2].

w 85.

does

(A)

(A)

84.

transform

~J=~

~

~J=~

(D)

[cJ

= [c,']

A common method of image sampling is to (A)

compress the image

(B)

segment the image

(C)

scan the image

(D)

watermark the image

12

86.

87.

88.

The enhancement process is helpful in (A)

increasing the inherent information content in the data

(B)

increasing the dynamic range of the inherent information content in the data

(C)

both (A) and (B)

(D)

none of the above

Which of the following property of median filter is not correct? (A)

It is a linear filter

(B)

It is useful for removmg isolated lines or pixels wh1le preserving spatial resolutions

(C)

Its performance is poor when the number of noise pixels in the window is greater than number of pixels in the window

(D)

None of the above

The contrast ratio is defined as (A)

89.

90.

91.

92.

93.

y

= ai).l

(B)

y

= ).lia

(C)

y =a x

According to Shannon's compression c, is given by

noiseless coding theorem,

(A) c= B x H

c

(B)

=H

+e

(C)

(D) y =(a x ).1) 2

).l

the

maximum

c= BIH

(D) c

achievable

= H /B

In Transform coding, compression is achieved by (A)

exploiting redundancy in the data

(B)

ignoring the inter pixel dependencies

(C)

transforming the given image into another array

(D)

none of the above

Run-length coding fall under the following image compression technique? (A)

Pixel coding

(B)

Predictive coding

(C)

Transform coding

(D)

Hybrid coding

The quantizer should be designed to limit the (A)

Granularity

(B)

Slope overload

(C)

Edge-busyness

(D)

All the above

The feasible region represented by the constraints X1-xz<=l, X!+x2>=8, x,>=O, xz>=O of the objective function Max Z=3x,+2xz is (A)

A polygon

(B) . Unbounded feasible region

(C)

A point

(D)

13

None of these

138

94.

95.

96.

97.

If the pixels of an image are shuffled then the parameter that may change is

(A)

Histogram

(B)

Mean

(C)

Entropy

(D)

Covariance

The quantiser in an image-compression system is a (A)

Lossy element which exploits the psychovisual redundancy

(B)

Lossless element which exploits the psychovisual redundancy

(C)

Lossy element which exploits the statistical redundancy

(D)

Lossless element which exploits the statistical redundancy

The colour of an object is largely determined by its diffuse reflection coefficient. If Kd = (0.8, 0.4, 0), then what shall be the colour of the object, if the light used is blue and magenta ? (A)

White and Red

(B)

Red and Blue

(C)

Black and White

(D)

Black and Red

Separating the object from the background of an image is called (A)

Smoothing

(C). Thresholding 98.

99.

(B)

Spatial filtering

(D)

Spatial averaging

The process of recovering the input of a system from its output is called (A)

Inverse filtering

(B)

Wiener filtering

(C)

Median filtering

(D)

Mean filtering

The spatial interaction of luminances from an object and its surround creates a phenomenon called the (A)

Photopic vision

(B)

Scotopic vision

(C)

Match band effect

(D)

Dithering

100. Reduction in number of bits in an image is called

138

(A)

Image restoration

(C)

Image enhancement

14

(B)

Image compression

·(D)

Image segmentation

ENTRANCE EXAMINATION FOR ISSION, MAY 2012. Ph.D. Electronics Engineering COURSE CODE : 166 Number :

L l_ _ _ _ _ _ _ .

Signature of the lnt•igilatcr (wtth date)


Max : 400 Marks

Instructions to Candidates: 1.


2.


3.


-!.

Avoid blind guessing A wrong answer will fetch you -1 mark and the correct answer will fetch 4 marks.

5.


6.


7.

Do not attempt to answer after stop signal is given. Any such attempt will disqualify your candidature

8.

On st-op signal, keep the question paper and the answer sheet on your table and wait for the invigilator to collect them.

9.

Use of Calculators. Tables, etc. are prohibited.

1.

Radar range primarily depends upon (A) Peak transmitted power (C) Square of transmitted power

(B) (D)

Average transmitted power Independent of transmitted power

2.

One method of solving 'blind speed' problems is to (A) use a variable PRT (B) change Doppler frequency (C) use digital MTI (D) use short wavelength

3

The type of modulation scheme used in Iridium system is (A)

4.

5.

16-PSK

(B)

BPSK

Earth station figure-of-merit is defined as (A) 10 log(GIT) (B) 10 Ln(GIT)

QAM

(D)

(C)

10 log (GT)

(D)

20 log(GIT)

(D)

Elliptical

(D)

365 days

When the orbit eccentricity(e) equals zero, the orbit is (A) A parabola (B) Circular (C) A hyperbola

6.

Satellite capacity depends on (A) Weight that can be placed in orbit (B) area available for energy dissipation (C) Transmitter power (D) All the above

7.

Synchronous satellites orbit the earth once in (A) 1 hour (B) 24 hours ' (C)

8.

10 hours

When r is the radius of circular orbit of a satellite, then orbital period of the satellite is proportional to (A) (C)

r ,~, 2

9.

Which of the following diode is used as detector in radar? (A) Gunn diode (B) Schottky diode (C) Zener diode (D) IMPA'IT diode

10.

The resolution of a pulsed radar can be improved by (A) decreasing pulse width (B) increasing pulse width (C) increasing the pulse amplitude (D) decreasing the pulse repetition frequency

166

QPSK

(C)

2

11.

Which of the following i6 not limitation of A.\iPS? (A) hmiled spectrum (B) poor privacy protection (C) low calling capacity (0) wide coverage area

12.

The type of handoff used in COMA aS-95) system (Al Soft handoff (BJ Hard handoff
13.

The access method used in OECT system is (A) FDMAfi'DD (B) 1'0l\1AJTDD (C) FDMA/FDD (D) TDMNFDD

14.

Larger cells are more useful in (A) densely populated urban areas (Cl rural areas

15.

(B) (0)

lightly populated urban areal! mountain areas

Tht~

modulation scheme used in GSM system (AJ QPSK (B) (C) GMSK (D)

QAM FSK

16.

If the bandwidth of th~ si!!nal is lesser than the bandwidth of the channel, then the type of fading is (AI Fast fading (B) Flat fading (C) Slow fading (0) None of the above

17.

Hata model is valid from (A) 1500MHz to 2000MHz (C) 150MHz to 1500Mllz

(B) (0)

l50MHz to 1920 MHz None of the above

18.

Wh1ch of the outdoor model is known as ITS irregular terrain model? (A) Okumura model (Bl Hata model (C) PCS model (0) Longley Rice model

19.

The other name for Antenna diversity (A) Frequency divllrsity (C) Time diversitY

20.

A baud is a unit of (A) Channel capacity (C) Signaling speed

(B) (D)

Space diversity Hybrid diversity

(B)

Information None of the above

(0) 3

166

21.

Which of the following material is having the highest refractive index? (A) (C)

22.

23.

24.

diamond water

(B) (D)

Optical core can be satisfactorily operated if (A)

Rl of the core is lesser than that of cladding

(B)

RI of the core is greater than that of cladcling

(C)

RI of the core is equal to that of cladcling

(D)

None of the above

Function of receiver in optical fibre is to (A)

reshape the degraded signal only

(B)

only amplify the degraded signal

(C)

both amplify and reshape of the degraded signal

(D)

none of the above

Total internal reflections can take place when light travels f-rom (A)

Air to glass

(B)

Water to glass

(C)

Air to water

(D)

Diamond to glass

25.

The color of a LED can be changed by (A) Using different band gap semiconductor (B) Changing the doping level of semiconductor (C) Increasing applied voltage (D) None of the above

26.

Which of the following device is more sensitive? (A) PIN diode (B) (C) Neither (A) or (B) (D)

27.

(C)

166

APD Either (A) or (B)

Which of the following is not applicable for LASER? (A)

28.

air glass

Provision for confinement No tuning arrangement

Loss in fibre is not due to (A) Impurities (C) Attenuation in fibre

(D)

Higher emission efficiency Narrow spectral width

(B) (D)

Micro bending Stepped index operation

(B)

29.

The cable that offers lowest dispersion is (A) SMSI (C) MMSI

(B) (D)

MMGI None of the above

30.

Q-switched LASER is (Al Continuous LASER (B) Short burst LASER (C) LASER produced by switching operation (D) Low powered laser

31.

In a receiver the input signal is 100 11 V, while the internal noise at the input is 1011 V With amplification the output signal is 2 V. while the output noise is 0.4 V. The noise figure of receiver is (A) 2 (B) 0.5 (D) None of the above
32.

A receiver is operated at a temperature of 300 K. The ~rans1stor used in the receiver have an average output resistance of 1 kn. The Johnson noise voltage for a receiver with a bandwidth of 200kHz is

(A) 1.8 nv cc) 4.3nv

8.4 nv

(D)

12.6 nv

33.

A speech signal has a total duration of 20 Sec. It is sampled at the rate of 8 kHz and then PCM encoded. The signal-to-quantizat.ion noise ratio is required t.o be 40 dB. The minimum st.orage capacity needed to accommodate this signal is (A) 1.12 KBytes (B) 140 KBytes (C) 168 KBytes (D) None of the above

3,1.

In a PCM system. if the rode word length is increAsPd from quantization noise ratio improve~ by the factor (A)

(C)

8/6 16

(B)

12

(D)

8

n to 8 bits, the signal to

35.

A slow FHJMFSK system has the following parameters Number of bits per MFSK symbol= 4. Number of MFSK symbol per hop= 5. The processing gain of the system is lA} 13.4 dB (B) 37.8 dB (D) 26 dB (C) 6 dB

36.

A transmitting antenna with a 300 MHz carrier frequency produces 2 kW of power Tf both antennas has unity power gain. the power received by another antenna at a distance of 1 km is (A)

ll.SmW

(B)

18.4m W

(C)

8.4pW

(D)

12.7 pW

5

166

37.

The radiation resistance of an antenna is 63 n and loss resistance 7 n. If antenna has power gain of 16, then directivity is (A) 48.26 dB (B) 12.5 dB (C) 38.96 dB (D) 24.7 dB

38.

An antenna is desired to operate on a frequency of 40 MHz whose quality factor is 50. The bandwidth of antenna is (A) 5.03 MHz (B) 800kHz (C) 127kHz (D) None of the above

39.

A thin dipole antenna is A./15 long. If its loss resistance is 1.2 (A)

41.1%

(C)

74.5%

(B) (D)

n, the efficiency is

59%

25.5%

40.

The air filled cavity resonator has dimension a = 3 em, b = 2 em, c = 4 em. The resonant frequency for the TMuo mode is (A) 5 GHz (B) 6.4 GHz (C) 16.2 GHz (D) 9 GHz

41.

Ionospheric preparation is not possible for microwaves because:

42.

(A)

Microwave will be fully absorbed by the Ionospheric layers

(B)

These will be an abrupt scattering in all directions

(C)

Microwaves will penetrate through the Ionospheric layers

(D)

There will be dispersion of microwave energy

A waveguide section in a microwave circuit will act as a (A)

(C)

43.

(C)

166

(B) (D)

Band filter Band Stop filter

Which one of the following is a transferred electron devices? (A)

44.

Low filter High filter

BARITT diode Gunn diode

(B) (D)

IMPATT diode Step recovery diode

In a microwave test bench, why is the microwave signal amplitude modulated at 1kHz? (A) To increase the sensitivity of measurement (B) To transmit the signal to a far·off place (C) To study amplitude modulation (D) Because crystal detector fails at microwave frequencies

6

45.

46.

47.

Consider a 150 m long air-filled hollow rectangular waveguide with cutoff frequency 6.5 GHz. If a short pulse of 7.2 GHz is introduced into the input end of the Ktnde. the time taken by the pulse to return the input end is (A)

920 ns

(8)

460 ns

(C)

230 ns

(0)

430 ns

A film mtegrated circuit is

(A)

MMIC

(8)

HIC

(C)

Not useful at microwave frequency

(D)

Oir~ct

(8)

Cu

(01

SiO

Substrate material m MMIC is (A) Glass (C)

48.

Conductor material in 1\l.MJC is (A)

(C) 49.

(C)

51.

Alumina GaAs

(8)

Ag

(D)

SiO

(Bl

Epitaxial growth A method of lithography

Diffusion is (A)

50.

Gold

circuit

The same as evaporation Adding dopant~

(D)

Lithography is (A)

The process of deposition

(B)

The process of evaporation

(C)

The process of transferring patterns of geometric shapes

(01

The process of etching

A 2 kW earner 1s to be modulated to a 90% level. The total transiDitted power would

be (A)

(C)

52.

3.62kW 1.4 kW

(B)

2.81 kW

(D)

None of the above

A modulating signal is amplified by a 80% efficiency amplifier before being combined with a 20 kW carrier to generate an AM: signal. The required DC input power to the amplifier, for the system to operate at 100% modulation, would be (A)

5 kW

(b)

8.46 kW

(C) 7

12.5 kW

(D)

6.25 kW

166

53.

If the modulation index of an A.l\1 wave is changed from 0 to t, the transmttted power (A) increases by 50% (B) inrreases by 75% (C) increases by 100% (D) remains unaffected

54.

An AM signal is detected using an envelope detector. The carriE'r frequency and modulating signal frequency are 1 MHz and 2kHz respectively. An appropriate valut> for the time constant of the envelope detector i~ (A)

55.

59.

695kHz

Parabolic dish

g.,/gd

For a 100

(D)

lp sec

(B)

700kHz

(C)

705kHz

(D)

710kHz

(B) Dipole

(C)

Yagi-uda

(D)

Hehcal

(B)

gc!lgp

(C)

g.

(D)

grt

(D)

.VB

(Dl

25 W

(D)

112"

n antenna w1th 2 A of current, the radiated power is

400 W

(B)

200 W

(C)

50 W

Hnlf wave beamwidth of optimum flare horn in E-plane is (A)

61.

0.2 p Sec

Antenna radiation efficil'ncy is high when its length is (A) ..i (B) ..i/2
(A)

60.

(C)

Antenna efficiency is (A}

58.

20 p Sec

CU'cularly polarized antenna is (A)

57.

(b)

For an AM signal, the bandwidth is 10 kHz and the highest frequency component present is 705kHz. The carrier freq\tency used for this AM signal iR (A)

56.

500 p Sec

56 A. IdE

(B)

28-i/dE

(C)

122-i/dE

If the impedance of a transmission line is 1.119 p Him and the capacitance is

12.3 PF/m, the time requll'ed for the wave to travel 1 m length of the hne is (A) 62.

(C)

3. 71 ns

(D)

3. 71 m~;

An amplifier

(B) An oscillator (C)

Mixer

(D)

A filter

533:0

(D)

812:822

H-plane Tee JUnction (A)

166

(B) 0.0371 ms

Magic Tee is used as (A)

63.

0.371 nm

813

=823

(B)

831

=823 8

(C)

64.

For a reciprocity network (A)

65.

71.

73.

(B)

~2e/ mub

(C)

~2mleub

(D)

~1/2e/mrl0

V0 I ~c,ff

(B)

A.ol..fi:

2.451 nH/mil

(B)

1.366 nH/mil (C)

1000 mH/mil

(D)

10 nH/mil

1.68

n

0.2340

(C)

0.1680

(D)

0.01680

(B) Barnes

(C)

Engelmann

(D)

Wen

(B)

Barrett

Important plat forms for RFMEMS is (A)

Coaxial line

(B)

Two wi1·e line

Planar· hne

(D)

Parallel plate line

The distribution function of a random variable is obtained by probability density function. (A)

72.

~2elm~

Microstrip line invented by (A)

70.

Su = 81;

The dimensions of the parameters of a gold planar resistor are 1 = 11 m, d = 0.2 p m. w = 8 mm and its resistance is (A)

69.

(C)

Round wire inductor has 1 = 100 mils, d = 10 mils and its inductance is

68.

S•; =sji

Wavelength ofMicrostrip line is (A)

67.

The electron velocity in reflex klystron is (A)

66.

S,; = S11

Differentiation

(B)

Integration

(C)

Multiplication

t.he (D)

Division

A probability function is given by p(0)=0.3164. p{1)=0.4219. p{2)=0.2109, p(3)= 0.0469 and p(4)= 0.0039. Find its mean and variance.

(A)

1.000, 0.750

(B)

1.500, 3.250

(C)

1.000, 0.500

(D)

None of the above

Let 'E' bean event and Jet EC be its complement. If P(E) =1/3, then (A)

P(E•) = 1/3

(B)

P(E<)c: 5/6

9

(C)

P(E•)

=2/3

(D)

P(E')= 1/6

166

74.

Let 'X' be a discrete random variable. Denote its distribution function by Fx(x). If Fx(2) 1/3 and Fx(3) = 213. then

=

(A) (C)

P(2SX<3)=113 P(X<2)=113

(B) (D)

P(X2:2)=113 P(2<Xs3)=113

75.

Tickets numbered 1 to 20 are mixed up and then a ticket is drawn at random. What is t.he probability that the ticket drawn has a number which is a multiple of 3 or 5'? (A) 215 (B) 112 (C) 9120 (D) 8/15

76.

A Vector space consisting o f - - - - - - vectors is called Trivial Vector space. (A)

3

(B)

2

(C)

0

(D)

I

77.

Suppose a population is normally distributed with a mean of 200 and a standard deviation of 40. The probability that x < J 50 is (A) 0.1056 (B) 0.1438 (C) 0.1634 (D) 0.3944

78.

Which two distributions are useful in analyzing waiting lines or "queues"? (A)

(C) 79.

Binomial and Poisson Poisson and exponential

(B) (D)

Binomial and normal Exponential and normal

A standard normal distribution has a mean of deviation of (A) 0,0 (B) 0,1 (C) 1,1

and standard (D)

1,0

80.

If a random variable X has a uniform distribution with a mean of 10 and the lowest vnlue of xis 5, what is the largest value of x that can exist'? (Al 5 {B) 10 (C) 15 (D) 20

81.

An in1age function f(x,y) is characterized by f(x,y)= i(x,y) r(x,y) where

82.

83.

M6

(A)

0 < f(x,y )< oo

(B)

0 < f(x,y }< 1

(C)

l

(D)

0 <255

(C)

Smoothening

Sampling of an image is required for (A) Quantization (B) Sharpening

The use of Translation property of Fourier transform is (A) Centering the low frequency component (B) Centering the DC component (C) Centering the high frequency component (D) All the above

W

(D)

Digitization

84.

To modify and prepare the pixel values of a digitized image to produce a form that is more suitable fix subsequent operations within the generic model, Image - - - - - - - technique is used. (A) Restoration (B) Segmentation (C) Enhancement (0) Compression

85.

To find the bright points in an image, - -- - - - - smoothing filter should be used. (A) Mean (B) Median (0) Minimum (C) Maximum

86.

Consider a gray scale image and apply log transformation with a scaling constant of 1.5. How will the resultant image look like?

(A) (C)

87.

89.

90.

91.

(B) (0)

low contrast image low brighten image

Assume that a digital image of size 50 x 50 is corrupted with impulse noise of 0.15. Approximately how many pixels are corrupted with noise? (A)

88.

high contrast image high brighten image

625

(B)

750

(C)

1000

(D)

1500

The concept behind law of large numbers is used t o - - - - - - - in an image. (A)

Reduce noise

(B)

Perform segmentation

(C)

Perform Compression

(D)

None of the above.

A pixel p at coordinates (x, y) has four horizontal and vertical neighbours whose coordinates are given as (A)

(X+l.y+l), (x,y+l), (x-1,)•-1), (x.y-1)

(B)

(x+l,y+l), (x+l,y-1), (x-l,y+l), (x-l,y-1)

(C)

(x+l,y), (x-l,_v), (x+l,y+l). (x-l.y-1)

(D)

(x+l,y). (x-l,y). (x,y+l), (x,y-l)

The Ds distance (Chessboard distance) between p and q with coordinates (x, y) and (s, t) is defined as (A)

jx-sj+ly- tj

(B)

Max ~x- sj,jy - tl)

(C)

Min ~x-sj,jy-tj)

(D)

jx- sj2 +jy -tj2

An offset error in a DAC will show up as an incorrect analog output-------

(A)

Only for higher input values

(B)

Only for lower input values

(C)

Only for certain (scattered) inputs

(D)

For all inputs

11

166

92.

Of the methods listed, the fastest AID conversion is done by a - - - - - - (A) Single slope ramp converter (B) Dual slope ramp converter (C) Successive approximation converter (D) Tracking converter

93.

Convolution is used to find (A) The impulse response of an LTI System (B) Frequency response of a System (C) The time response of a LTI syst.em (D) 1'he phase response of a LTl system

94.

The spectral density of white noise is (A) Exponential (B) Uniform

(C)

Poisson

(D)

Gaussian

95.

IJR fllters (A) use (B) are sometimes called recursive filters (C) can oscillate if not properly designed (D) all the above

96.

Coefficient symmetry is important in FIR filters because it provides (A) a smaller transition bandwidth (B) less band ripple (C) less stopband ripple (D) a linear phase response

97.

If a linear phase filter has a phase response of 40 degrees at 200Hz, what will be its

phase response be at a frequency of 400Hz (assuming that both frequencies are in the band of the filter)? (A) 35 degree (B) 40 degree (C) 45 degree (D) 80 degree

98.

The final value of x(t)=[2 + e-31] u(/) (A)

99.

2

(B)

(C)

3

e~1<

(D)

A DSP convolves each discrete sample with these coefficients : -0.25, -0.25, 1.0, -0.25 and -0.25. This must be a (A) low filter (B) high filter (C) band filter (D) band stop filter

100. The basic proceHs thnt's going on inside a DSP chip is (A) Quantisation (B) MAC (C) Logarithmic calculation (D) vector calculations

166

0

12

ENTRANCE EXAMINATION FOR ISSION, MAY 2013. Ph.D. (ELECTRONICS ENGINEERING) COURSE CODE: 166 Number :

IL______

...J

Signature of the Invigilator (with date)


Max : 400 Marks



2.


3.


4.


5.


6.


7.


8.


9.


1.

2.

Two independent random variables X and Yare uniformly distributed in the interval [-1,1]. The probability that max [X,Y] is less than 112 is (A)

3/4

(B)

9/16

(C)

114

(D)

2/3

1 2 Given f(z) = - - - --. If Cis a counter clock wise path in the z-plane such that z+l z+3 jz + lj = 1 , the value of

3.

2~ ff(z )dz is

(A)

-2

(B)

-1

(C)

1

(D)

2

Let be the solution of the initial value problem dy = (y 2 +x}y(O)= 1. Using Taylor dx

series method of order 2 with the step size h = 0.1, the approximate value of Y(O.l) is

4.

5.

6.

7.

166

(A)

1.315

(B)

1.415

(C)

1.515

(D)

1.215

The number of irreducible quadratic polynomials over the field of two elements F2 is (A)

0

(B)

1

(C)

2

(D)

3

The initial value problem x dy = y + x 2 , x)O; y(O) = 0 has . dx (A)

Infinitely many solutions

(B)

Exactly two solutions

(C)

A unique solution

(D)

No solution

In modern MOSFET, the material used for the gate is (A)

Heavily doped polycrystalline silicon (B)

High purity silica

(C)

High quality silicon

Epitaxial grown silicon

(D)

The potential divider bias is more commonly used because it (A)

Uses minimum circuit components

(B)

Stabilizes the collector current

(C)

Does not reduce the input and output impedances drastically

(D)

Uses only one battery 2

8.

9.

10.

A two stage amplifier with negative has an overshoot when the damping factor K is emitter follower circuit is widely used in electronic instruments because (A)

Less than unity

(B)

Greater than unity

(C)

Negative

(D)

Zero

The propagation delay of ECL family is (A)

10nsec

(B)

4nsec

(C)

2nsec

(D)

30nsec

The fan-out of TTL family is (A)

20

(B)

50

(C)

10

(D)

40 1

11.

The eigenvalue A of the following Fredholm integral equation y(x)= A Jx 2 ty(t)dt is 0

12.

13.

14.

15.

(A)

-2

(B)

(C)

4

(D) -4

2

d2y

Let y be the solution of the initial value problem - + y = 6cos 2x, y(O) dx 2 y y 1 (0) =1. Let the Laplace transform of y be F(s). Then, the value of F(1) is (A)

17/5

(B)

13/5

(C)

1115

(D)

9/5

= 3,

The stack pointer in a microprocessor (A)

Keeps the address of the next instruction to be fetched

(B)

Holds the address of the top of the stack

(C)

Counts the number of programs being executing on the microprocessor

(D)

Counts the number of instructions being executing on the microprocessor

The type of duplex method in CDMA2000 is (A)

FDD

(B)

TDD

(C)

FDDfrDD

(D)

None of the above

Okumura model is applicable for frequencies in the range of (A)

1500MHz to 2500MHz

(B)

150MHz to 1920 MHz

(C)

150MHz to 1500MHz

(D)

None of the above

s

166

16.

17.

18.

19.

20.

21.

What makes optical fibers immune to EMI? (A)

They transmit signals in as light rather than electric current

(B)

They are too small for magnetic fields to introduce current in them

(C)

Magnetic fields cannot penetrate the glass of the fiber

(D)

They are readily shielded by outer conductors in cable

Which of the following is not a reason to use fiber-optic cables for point to point data transmission? (A)

Need to assure data security

(B)

Avoidance of ground loops

(C)

Data-transfer rates too low to use metal cables

(D)

Elimination of spark hazards

Which of the following describes a technique to achieve fault tolerance in optical networks with minimum costs? (A)

Bying active elements

(B)

Avoid the usage of star couplers

{C)

Duplication of system properties

(D)

Topological reconfiguration

A normal GSM has 3 start bits, 3 stop bits, 26 training bits for allowing adaptive equalization, 8.25 guard bits and 2 bursts of 58 bits of encrypted data which is transmitted at 270.833 kbps in the channel. Calculate frame rate. (A)

417.66 frames/sec

(B)

216.66 frames/sec

(C)

318.66 frames/sec

(D)

519.66 frames/sec

The speech coding used in D-AMPS is (A)

QCELP

(B)

RPE-LTE

(C)

VSELP

(D)

None of the above

One method of solving 'blind speed' problems is to (A)

Use a variable PRT

(B)

Use digital MTI

(D)

Use short wavelength

.

(C) 22.

166

Change Doppler frequency

The noise figure of a radar receiver is 12 dB and its bandwidth is 2.5MHz. The value of P min for the radar will be (A)

1.59 x 10-9 W

(B)

1.59 x 1Q-I5 W

(C)

1.59x1Q-I7W

(D)

1.59 x

4

1()-13 W

23.

24.

25.

26.

27.

28.

29.

30.

A communication channel has bandwidth of 5KHz and if signal-to-noise ratio is 5,the corresponding channel capacity will be (A)

18000 bits/sec

(B)

4000 bits/sec

(C)

1500 bits/sec

(D)

1000 bits/sec

The type of light source and fiber chosen for FDDI networks are: (A)

Single-mode fiber and 1550-nm lasers

(B)

Single-mode fiber and 1300-nm lasers

(C)

Multi-mode fiber and 1300-nm lasers

(D)

Multi-mode fiber and 1300-nm LEDs

Speeds of laboratory fiber optic Local Area Networks are now in the range of (A)

1 Mbits/s

(B)

10 Mbits/s

(C)

Gigabits per second

(D)

Hundreds of megabits per second

A device used to display one or more digital signals so that they can be compared to expected timing diagrams for the signals is: (A)

DMM

(B)

Spectrum Analyzer

(C)

Logic Analyzer

(D)

Frequency Counter and the OR function can be used to

The AND function can be used to

(B)

(A)

Enable, Disable

(C)

Enable or Disable, Enable or Disable (D)

Disable, Enable Detect, Invert

In a 16-bit Johnson counter sequence there are a total of how many states or bit patterns? (A)

2

(B)

6

(C)

12

(D)

24

How is a J-K Flip-Flop made to toggle? (A)

J=O, K=O

(B)

J=1, K=O

(C)

J=O, K=1

(D)

J=1, K=1

ALM is the acronym for (A)

Array Logic Matrix

(B)

Arithmetic Logic Module

(C)

Asynchronous Local Modulator

(D)

Adaptive Logic Module

5

166

31.

Find the node voltage VA Rl

••ll

VA

R3

SOil

RZ

- ~VSl =._12V

Z41l

~vsz ~

6V

VB

32.

(A)

6 volts

(B)

12 volts

(C)

4.25 volts

(D)

3.25 volts

A 15

n

resistor, a 220 pH coil, and a 60 pF capacitor are in series across an ac

source. What is the bandwidth of the circuit?

33.

34.

35.

(A)

138 MHz

(B)

10,866 Hz

(C)

1,907 Hz

(D)

138KHz

To tune a parallel resonant circuit to a higher frequency, the capacitance should be (A)

Increased

(B)

Decreased

(C)

Left Alone

(D)

Replaced with inductance

In the ionosphere layer, the lowest frequency signal that penetrates the layer upon vertical incidence is given by (A)

h

(C)

{L ~ ~81N Max

166

NMax

~ 81N 2 Max

(B)

{L

(D)

h = 81 ~NMax

In superheterodyne receiver, the frequency of local oscillator (A)

Equal to that of incoming signal

(B)

Slightly less than that of incoming signal

(C)

Half that of incoming signals

· (D) 36.

~81

Higher than that of incoming signal

In which header file is the NULL macro defined? (A)

stdio.h

(B)

stddef.h

(C)

stdio.h and stddef.h

(D)

math.h

6

37.

A pointer is (A) A keyword used to create variables (B) A variable that stores the address of an instruction (C) A variable that stores the address of other variable (D) All the above

38.

The library function used to find the last occurrence of a character in a string is (A) strnstr( ) (B) laststr( ) (C) strrchr( ) (D) strstr( )

39.

All MATLAB variables are -----array (A) One Dimensional (B) (D) (C) Multidimensional

Two Dimensional All the above

40.

The MATLAB function used to generate " 0 0 0 0 0 " as output is (A) z =zeros (5,1) (B) z =zeros (1,5} (C) z = zeros (1 x 5) (D) z = zeros (5x 1)

41.

Special transmission lines constructed with copper patterns on a printed·circuit board that can be used as tuned circuits, filters, or impedance-matching circuits are called (A) Microchip (B) Stripline (C) PCB lines (D) Special lines

42.

Tinier Microstrip and striplines made by using monolithic, thin-film, and hybrid techniques when combined with diodes, transistors, and other components form what are called (B) microwave integrated circuits (A) Microstrip integrated circuits (D) high-frequency integrated circuits (C) Stripline integrated circuits

43.

Find the transit time at the cavity gap for a two-cavity klystron operating at 5GHz with de beam voltage of 10KV and cavity gap of 2mm. The magnitude of the gap voltage is 100 volts for a given input RF voltage. (A) 33.7x 1Q-12sec (B) 3.37 x 1Q~ 9 sec (C) 2.68 x 10~9 sec (D) 26.8 x 10~ 12 sec

44.

Potential energy----- if the test charge is moved from a lower potential point to a higher potential point (B) Increases (A) Remains the same (D) Becomes zero (C) Decreases

45.

In the case of a linear material medium, - - - - - equation can be derived easily from Gauss law (B) Laplace (A) Poisson (D) None of the above (C) Both (A) and (B) 7

166

46.

47.

Z-transform of unit impulse function is (A) z

(B)

z2

(C)

(D)

1

(B) (D)

1/2 -1/2

0

Inverse Z-transform (A)

2

(C)

-2

of~ is (z -1)

48.

A regression model is used to express a variable Y as a function of another variable X. This implies that (A) There is a causal relationship between Y and X (B) A value of X may be used to estimate a value of Y . (C) Values of X exactly determine values of Y (D) There is no causal relationship between Y and X

49.

IfM= {1, 3, 5, 7, 9}, N= {2, 5, 7} and 0= {5, 6} then MnN UO (A) {5} (B) {5, 6, 7} (C) {1, 2, 5, 6, 7, 9} (D) {1, 2, 9}

50.

In Cisco's Unified Wireless Solution, what is the split-MAC architecture? (A) The split-MAC architecture uses MAC addresses to create a forward/filter table and break up collision domains. (B) The split-MAC architecture allows the splitting of 802:11 protocol packets between the AP and the controller to allow processing by both devices (C) The split-MAC architecture uses MAC addresses on the wireless network and IP addresses on the wired network (D) The split-MAC architecture uses MAC addresses to create a forward/filter table and break up broadcast domains.

51.

is used to quantify how strongly transmitted ultrasound amplitude decreases as a function of frequency (A) Attenuation co-efficient (B) Reflection co-efficient (C) Pearson co-efficient (D) None of the above

52.

Changing wave angle with frequency is a mechanism for - - - - (A) Group velocity dispersion (B) Waveguide dispersion (C) Both (A) and (B) (D) None of the above

53.

Which of the following is not found on the linear scales printed at the bottom of Smith charts? (A) SWR (B) Impedance (C) dB loss (D) Reflection coefficient

166

8

54.

What is the frequency range of the IEEE 802.11a standard? (A) 2.4 Gbps (B) 5 Gbps (C) 2.4 GHz (D) 5 GHz

55.

Compression in PCM refers to relative compression of (A) Lower signal frequencies (B) Higher signal frequencies (C) Higher signal amplitudes (D) Lower signal amplitudes

56.

An antenna in free space receives 2 f.1. W OF POWER WHEN THE INCIDENT ELECTRIC FIELD IS 20mV/m (rms). The effective aperture of the antenna is (A) 1.885 m2 (B) 3.77 m 2

(C)

0.005 m2

(D)

0.06m2

57.

The line-of-sight communication requires the transmit and receive antennas to face each other. If the transmit antenna is vertically polarized for best reception the receive antenna should be (A) At 45° degrees w.r.t horizontal polarisation (B) At 45° degrees w.r.t vertical polarisation (C) Horizontally polarized (D) Vertically polarized

58.

Consider a losseless antenna with a directive gain of +6dB. If 1 m W of power is fed to it , then the total power radiated by the antenna will be (A) 10 mW (B) 8 mW (C) 6 mW (D) 4 mW

59.

A transmitting antenna having an effective height of 125 m take a current of 50 amp (rms) at a wavelength of 1250m. The antenna efficiency for a total antenna loss resistance of 5 ohms is (A) 62% (B) 72% (C) 82% (D) 92%

60.

A transmission line is feeding 1W of power to a horn antenna having a gain of 10 dB. The antenna is matched to the transmission line. The total power radiated by the horn antenna into the free-space is (A) lW (B) lOW (C) O.OlW (D) 0.1 W

61.

Figure merit is always unity in (A) SSB-SC

(B)

AM

(C)

(D)

All the three

FM

9

166

62.

The sampling rate is always between (A) Oand 1 W (C) 2Wto 4W

(B) (D)

1Wto2W None

63.

In a delta modulation scheme, the step height is 75 mV and step width is 1.5 ms. The maximum slope that the staircase can track is (A) 50 V/s (B) 55 V/s (C) 60 V/s (D) 65 V/s

64.

Which of the following pulse communication system is inherently immune to noise? (A) PPM (B) PCM (C)

PWM

(D)

PAM

65.

Which of the following gives maximum probability of error? (A) ASK (B) FSK (C) PSK (D) DPSK

66.

In a (A) (B) (C) (D)

67.

In closed loop control system with positive value of gain the overall gain of the system will be (A) Increase (B) Decrease (D) None of the above (C) Idle

68. (A) (C)

open loop control system Output is independent of control input Output is dependent of control input Only system parameters have effect on the control output None of the above

has tendency to oscillate. Open loop system Both (A) and (B)

(B) (D)

Closed loop system Neither (A) nor (B)

69.

The initial response when the output is not equal to input is called----(A) Transient Response (B) Error Response (C) Dynamic Response (D) Static Response

70.

- - - - - increases the steady state accuracy (A) Integrator (B) Qifferentiator (C) Phase lead compensator (D) Phase lag compensator .

71.

A system is said to be a casual system if the output depends on (A) Past input only (B) Present input and past output (C) Present input and future output (D) None of the above

166

10

72.

73.

The Discrete Time Fourier Transform for o(n) is (A)

1r

(B)

1

(C)

0

(D)

infinity

A causal system having the transfer function H(s)

=- 1 -

8+2

is excited with10u(t). The

time at which the output reaches 99% of its steady state value is

74.

75.

76.

77.

78.

(A)

2.9 sec

(B)

2.7 sec

(C)

2.5 sec

(D)

2.3 sec

In binary data transmission DPSK is preferred to PSK because (A)

A coherent carrier is not required to be generated at the receiver

(B)

For a given energy per bit, the probability of error is less

(C)

The 180° phase shifts of the carrier are unimportant

(D)

More protection is provided against impulse noise

The total bandwidth required for a raised cosine spectrum is

(A)

W/2

(B)

1W

(C)

2W

(D)

4W

For a CSMA/CD network, twice the propagation time between the two most distant stations is called (A)

Slot time

(B)

Transfer time

(C)

Round trip delay time

(D)

Both (A) and (C)

- - - - - is a technique which transforms an analogue telephone circuit into a digital signal, and involves three consecutive processes: sampling, quantization and encoding. (A)

Frequency Modulation (FM)

(B)

Pulse Code Modulation (PCM)

(C)

Amplitude Modulation (AM)

(D)

Phase Modulation (PM)

The sequence of the binary digits representing the outcomes of parity checks in Hamming codes is known as (A)

Look-up entry

(B)

Hamming distance

(C)

Radix

(D)

Syndrome

11

166

79.

Find the transit time at the cavity gap for a two-cavity klystron operating at 5GHz with de beam voltage of 10KV and cavity gap of 2 mm. The magnitude of the gap voltage is 100 volts for a given input RF voltage. (A) 33.7 x 10-12 sec (B) 3.37 x 10-9 sec (C) 2.68 x 10-9 sec (D) 26.8 x 10- 12 sec

80.

The maximum gain of 100 element uniform linear array is (A) 1 (B) 10 (C) 100 (D) 1000

81.

Rhombic antenna is (A) Standing wave antenna (C) .4/2 antenna

(B) (D)

Narrow band antenna Travelling wave antenna

82.

The number of log periodic antenna elements depends on (A) Gain only (B) Wedge angle only (C) Bandwidth only (D) Bandwidth, scale and space factors

83.

A Si microwave transistor has reactance 1 ohm, transit time cut-off frequency 4GHz, maximum E-field 1.6 x 105 V/m and saturation drift velocity 4 x 105cm/s. Determine the maximum allowable power (A) 6.48 Watts (B) 4.27 Watts (C) 2.64 Watts (D) 1.35 Watts

84.

The usage of multiple cavities in klystron improves (A) Impedance (B) Gain (C) Bandwidth (D) None of the above

85.

An air filled circular waveguide having an inner radius of 1 em is excited in dominant

mode at 10 GHz with x'n = 1.841. Find the guide wavelength of dominant mode. (A) 9.104 em (B) 8.223 em (C) 7.345 em (D) 6.303 em 86.

When a step-input is given to an op-amp integrator, the output will be (A) A ramp (B) A sinusoidal wave (D) A triangular wave with de bias (C) A rectangular wave

87.

In a full wave rectifier without filter, the ripple factor is (A) 0.482 (B) 1.21 (C) 1. 79 (D) 2.05

166

12

88.

89.

90.

91.

92.

93.

94.

95.

The minimum number of flip flops required to construct a mod- 75 counter is (A)

5

(B)

6

(C)

7

(D)

8

In a JFET, at pinch-off voltage applied on the gate (A)

The drain current becomes almost zero

(B)

The drain current begins to decrease

(C)

The drain current is almost at saturation value

(D)

The drain-to-source voltage is close to zero volts

The frequency of oscillation of a tunnel-collector having L = 30 f.IH and C = 300 PF is nearby (A)

267KHz

(B)

1677KHz

(C)

1.68 KHz

(D)

2.67 KHz

The type of modulation used in IEEE 802.15.4 having operating frequency of 2.4 GHz is (A)

DS-SS

(B)

BPSK

(C)

QPSK

(D)

OQPSK

The encryption standard used in HIPERLAN/2 is (A)

DES

(B)

RSA

(C)

ECC

(D)

RC4

The number bits used to denote the address of source and deBtination in IPv6 (A)

256 bits

(B)

128 bits

(C)

64 bits

(D)

32 bits

In a group of 10 servers, each is occupied for 30 minutes in an observation interval of two hours. Calculate the total traffic carried by the group. (A)

4.5E

(B)

3.5 E

(C)

2.5 E

(D)

32 bits

For a probability distribution, if 'a' is the mean, 'b' is the mode and 'c' is the standard deviation then the coefficient of skewness is (A)

(C)

(a-b)

(B)

c (a-c)

(D)

c

13

(b-a)

c (b -c)

a

166

96.

97.

98.

99.

Which one of the following is true regarding VLANs? (A)

Two VLANs are configured by default on all Cisco switches

(B)

VLANs only work if you have a complete Cisco switched internetwork. No off-brand switches are allowed

(C)

You should not have more than 10 switches in the same VTP domain

(D)

VTP is used to send VLAN information to switches in a configured VTP domain

What is the main reason the OSI model was created? (A)

To create a layered model larger than the DoD model

(B)

Application developers can change only one layer's protocols at a time

(C)

Different networks could communicate

(D)

Cisco could use the model

What protocols are used to configure trunking on a switch? (1)

VLAN Trunking Protocol

(2)

VLAN

(3)

802.1Q

(4)

ISL

(A)

1 and 2

(B)

3 and 4

(C)

1 only

(D)

2 only

How many broadcast domains are created when you segment a network with a 12·port switch? (A)

1

(B)

2

(C)

5

(D)

12

100. If standard deviation of data is 3, mean is 20 then coefficient of variation is

166

(A)

156

(B)

3/20

(C)

20/3

(D)

None

14

ENTRANCE EXAMINATION FOR ISSION, MAY 2010. Ph.D. (ELECTRICAL AND ELECTRONICS ENGINEERING) COURSE CODE: 141 Number:

~..!

_ _ _ _ __ _ ,

Signaluff of !he lnvigilalor (Wtlh date)


Max : 400 Marks


Write your Number within the box provided on the top of thls page and fill in the page 1 of the answer sheet usmg pen.

2.


3.

Read each question carefully and shade the relevant answer (A) or (B) or (C) or (D) in the relevant box of the ANSWER SHEET using HB pencil.

4.


5.

Do not write anything in the qut: rel="nofollow">stion paper. Use the whlte sheets attached at the end for rough works.

6.


7.

Do not attempt to !l\lswer after stop signal is given. Any such attempt will disqualify your candidsit:'ure. On stop signal, keep the question paper and the answer sheet on your table and wait for the invigilator to collect them. Use of Calculators, Tables, etc. are prohibited.

8.

9.

1.

2.

3.

4.

The intrinsic impedance of a lossy dielectric medium is given by (A)

(B)

(C)

(D)

In a hollow condncting sphere (A)

Electric field is zero

(B)

Electric field is a non-zero constant

(C)

Electric field changes with magnitude of the charge given to the conductor

(D)

Electric field changes with distance from the centre of the sphere

Consider the following statement.s regarding Maxwell's equations in differential form (symbols have the usual meanings) 1.

For free space

VxH =(tH }121£)£

2.

For free space

V.D=p

3.

For steady state current

VxH=J

4.

For Static electric field

V.D=p

(A)

1 and 2 are correct

(B)

2 and 3 are correct

(C)

3 and 4 are correct

(D)

1 and 4 are correct

In a right-handed cylindrical co-ordinate system, a, xa, = (A)

5.

141

H

a,

(B)

-a,

Kircbhotl's current law for direct currents is implicit in the expression (A)

V.D=p

(B)

(C)

V.B=p

(D) 2

jJ.ndf:O

dD VxH=J+df

6.

A circular loop has its radius increasing at a rate of 2 m/s. The loop is placed perpendicular to a constant magnetic filed of 0.1 wb/m2 • Wben radius of the loop is 2 m, the emf induced in the loop will be (A)

7.

O.SaV

(B)

Q.4aV

(C)

(D) zero

0.2JrV

The Fourier series expansion of a periodic function with half-wave symmetry contains only

CA) Sine (C)

8.

Even harmonics

40 Q

(B)

cc>

(20+j10) Q

(tO-j30)

n

(D) (1 O+j30) Q

""

(B)

1

J

(C)

0.5 J

(D)

0

A water boiler at home is switched on to the a.c. mains supplying power at 230 V/50 Hz. The frequency of instantaneous power by the boiler is (A}

11.

(D)

When a unit impulse voltage is applied to an inductor of 1 H, the energy supplied by the source is

(A}

10.

Cosine

In the delts equivalent of the given star connected circuit, ZQs is equal to

(A)

9.

Odd harmonics

(B)

0 Hz

(B)

50 Hz

(C)

100Hz

(D)

150Hz

The reciprocity theorem is applicable to (A)

Linear networks only

(B)

Bilateral networks only

(C)

Linear/bilateral networks

(D)

Neither of the two

3

141

12.

A sine wave voltage is applied across a capacitor; when the frequency of the voltage 15 increased, the current (A) increases (B) decreases (C) remains the same (D) is zero

13.

For a two-port bilateral network, the three transmission parameters are given by 6 17 I . A=-;B=andC=-. what IS the value ofD? 5 5 5 (A)

14.

15.

1

(B)

5

(C)

7 5

(D)

17 35

-

For a two-port network to be reciprocal (A)

z"=z:u

(B)

Y u=Yn

(C)

hll=-hl!

(D)

AD-BC=O

In the first foster form, the presence of first element capacitor C., indicates (A) pole at <.>=0 (B) pole at <.>= oo (C)

zero at w=:O

(D)

zero at w=:oo

16.

The transient current in a loss-free LC circuit when excited from an ac source is an - - - - - - sine wave. (A) undamped (B) overdamped (C) under damped
17.

Transient current in an RLC circuit is oscillatory when lA)

t8.

R=2~

(B)

R=O

(C)

R>Z~

(D)

R<2~

Two inductors are connected as shown in figure below. What is the value of the effective inductance of the combination? ~H

(A)

141

8H

(B)

10 H

(C)

4H

(D)

12 H

19.

The value of the resistance R in the circuit shown in the given figure is varied in such a manner that the power dissipated in the Sohm resistor is maximum. Under this condition, the value of R will be

... 2ov (A)

20.

3ohms

{B)

-L____3_...._.

9 ohms

(C)

12 ohms

(D)

6ohms

For the network shown in the figure below, what is the driving pomt impedance Z(s)?

---lr

1F

(A)

21.

22.

23.

In an unsaturated de machine armature reaction effect is (A)

demagnetizing

(B)

cross-magnetizing

(C)

magnetizing

(D)

kind of effect depends upon whether the machine is motoring or generating

The advantage of the double squirrel-cage induction motor over single cage rotor is that its (A)

efficiency is higher

(B)

power factor is hlgher

(C)

slip is larger

(D)

starting current is lower

A magnetic circu1t has a linear B-H curve with >.: 1.5 WbT at i stored in the field is (A)

24

(D) None of these

(C)

(B)

15 J

(B)

0.75 J

(C)

7.6 J

=10 A. The energy (D) 30 J

H the peak value of phase mmf is F ..... the peak value of the rotating field caused by

three-phase is (A)

(112) F....

(B)

F awr

(C)

5

(312) F....

(D) 3 F "'""

1.41

25.

'Crawling' in an induction motor is due to (A) Time harmonics in supply {B) Slip ring rotor Space harmonics produced by winding currents (D) Insufficient starting torque (C)

26.

In the bode· plot of a unity control system, the value of phase of GG<.l) at the gain cross over frequency is 125°. The phase margin of the system is (A)

27.

- 125"

(B)

-55°

(C)

55"

(D)

125•

Consider a system shown in the given figure

VC.)-ffi-C(.s.) II the system is disturbed so that c(O}=l , then c(t} for a unit step input will be (A)

28.

1+2t

(D)

1-2t

K

1

(B)

(C)

2

3

1

(D) 4

Three phase induction motor

(D) Synchronous motor

Signal flow graph is used to find (C)

Stability of the system Transfer function of the system

(B) Controllability of the system (D) Poles of the system

The eigenvalues of matrix given below is

(A)

141

(C)

The ac motor used in servo applications 1s a (A) Single-phase induction mot~r (B) Two-phw;e induction motor

(A)

31.

1· t

where K is the s +2s+K gain at the system in radians/ramp. For thls system to be critically damped, the value of K should be

(C)

:m.

(B)

The transfer function of a control system js given as T(s)

(A)

29.

1+t

·1,-2,-3

(B)

r: -~~ ll

1,2,3

(C)

6

1,-2,-3

(D)

-1,2,-3

32.

The matrix of any state-space equations for the transfer function C(s)/R(s} of the system shown below in the figure is

c.o)

(A)

33.

34.

-1 ( 0

0)

-1

(B)

('

0)

(C)

0 -1

(-I)

(D)

{3)

A linear discrete-time system has the characteristic equation, zl -0.8lz. The system (A)

is stable

(B)

is marginally stable

(C}

is unstable

(D)

stability cannot be assessed from the given information

For the transfer function G(s)H(s}

( )( ) . The phase cross-over frequency s s+l s+0.5

18

35.

0.707 radlsec

(A}

0.5 radlseo

(B)

(C)

1.732 radlsec

(D) 2 radlsec

For a unit step, a system with fo.rwa.rd path transfer function

2

? and the

s

path transfer function H(s)= (s+5), has a steady state output of (A)

36.

The

(B)

0

root

locus

plot

0.5

of the

(C)

system

0.2

having the loop

(D)

zero

transfer function

K G(s)H(s)= s(s+4)(sz+4s+5) has (A)

No breakaway point

(B)

Three real breakaway point

(C)

Only one breakaway point

(D)

One real and two complex breakaway point 7

141

37.

The main function of interpoles is to mmimize - - - - - b e tween the brushes and the commutation when the d.c. machine is loaded. (A)

38.

40.

42.

141

current

(D) wear and tear

low

{B)

(C)

zero

positive

(D) negative

54 N-m

(B)

81 N-m

(C)

108 N-m

(D)

None of the above

Retardation test on a d.c. shunt motor is used for finding ------losses. stray

(B)

copper

(C)

friction

(D) uoon

The maximum flux density in the core of a 250/3000 volts, 50 Hz single-phase transformer is 1.2 Wblm2, if the e.m.f. per turn is 8 volt, the primary and secondary turns respectively are {A)

32, 375

(B)

375.32

(C)

250,3000

(D)

None of the above

The regulation of a transformer in which the percentage resistance drops is 1% and percentage reactance drop is 5% for unity power factor is 1%

(B)

(C)

5%

6%

(D) 3.8%

A 3-phase induction motor is wound for 4 poles and is supplied from 50 Hz system, the rotor frequency when rotor runs at 600 rpm is (A)

44.

(C)

(A)

(A)

43.

sparking

A 220 V shunt motor develops a torque of 54 N-m at armature of 10 A The torque produced when the armature current is 20 A. is

(A)

41.

(B)

An ideal d.c. generator is one that h a s - - - - - voltage regulation. (A)

39.

friction

50 Hz

(B)

(C)

30Hz

60Hz

(D)

Non~

In the circle diagram of an induction motor, point of maximum input lies on the tangent drawn parallel to (A)

Output line

(B) Torque line

(C)

Vertical axis

(D)

8

Horizontal axis

45.

46.

A repulsion motor is equipped with (A)

a commutator

(B)

slip rings

(C)

a repeller

(D)

cogging

If, in an alternator, chording angle for fundamental flux wave is 51h harmonic is (A)

47.

48.

49.

25 a

(B)

index

(C)

instruction

(D)

program counter

(D) o/25

The used as a working area in U is (A)

Program counter

(B)

Instruction

(C)

Instruction decoder

(D)

Accumulator

A 32-bit microprocessor has word length equal to

2 bytes

(B)

1 byte

(C)

4 bytes

(D)

8 bytes

To represent number 33 in binary, number of bits required is 6

(B)

5

(C)

4

(D) 7

Short transmission line is represent by the lamped parameters R andL

(B)

Rand C

(C)

C and L

(D)

R, Land C

If R1 and R2 are the radius of sheath and conductor of a cable, then optimal ratio of the radius of the cable to the radius of the conductor is (A)

53.

(C)

accumulator

(A)

52.

o/5

(A)

(A)

51.

(B)

The used in the control unit of the U to indicate the next instruction which is to be executed is

(A) 50.

5a

a. its value for

Rz1R1

The dielectric loss in the insulation of the cable occurs due to (A)

Leakage current

(B)

Leakage voltage

(C)

Both (A) and (B)

(D)

None of the these

9

141

64.

65.

Factor aft'ecting the sag are/is (A)

length of span

(B)

working tensile strength

(C)

temperature

(D)

all the above

e /L ;=vc

The relation between traveling voltage (A)

56.

67.

Air break switch

(B)

Isolator

(C)

Oil switch

(D)

None of the above

62.

141

0

(B)

0.05 flH

(C)

0.1 !IH

(D) 0,05 m.H

An insulator bas 3 units and K = 118. The string efficiency will be 100/8%

(B)

100/3%

(C)

66.7%

(D) 84.3%

Which of the two generalized constant in a transmission are equal? Band C

(B)

(C)

A and D

A and B

(D) Band D

The coefficient of reflection of current for an open ended line is (A)

61.

ei=Ji.C

For a 1 m long conductor, the value of internal ind1.1cta.nce will be

(A)

60.

(D)

(A)

(A) 59.

ei=~

The equipment which is provided with arc horn is

(..<\)

68.

(B)

1

(B)

0.5

(C)

-1

(D) 0

Total induction of magnetically non coupled series inductor is calculated the same as (A)

Resistances in parallel-series

(B)

Resistances in parallel

(C)

Resistanr.es in series

(D) None of the above

Coefficient of coupling expresses (A)

a relatioilllhij> to flux density and magnetizing force

(B)

a fractional value of the total flux linking one circuit to another

(C)

a percentage

(D)

none of the above 10

63.

64.

65.

66.

67.

68.

69.

If the phase angle of a paraJJel RL circuit is -36", the circuit is (A)

more resistive than reactive

(B)

more reactive than resistive

(C)

equaJJy resistive and reactive

(D)

none of the above

In a series capacitive circuit, the smallest capacitance has (A)

the lowest voltage drop

(B)

the highest voltage drop

(C)

the same voltage drop as aJJ other capacitora

(D)

none of the above

Series or paraJJel resonant circuits can be used to create (A)

Low filters

(B)

Low and high filters

(C)

Band- and band·stop filters

(D)

All tbe above

In complex number, resistance is a real term, while reactance a/an

(A)

j term

(C)

Value appearing on the vertical axis (D) All the above

(B)

Imaginary term

When current dramatically increases, the voltage point on the diode forward V-I characteristic curve is called the (A)

Breakdown voltage

(B)

Knee voltage

(C)

Barrier voltage

(D)

Both (B) and (C) are true

Which point on the de load line result in an 1c

=VccfRc and V~ =0 V ?

(A)

Saturation point

(B)

Cutoff point

(C)

Q point

(D)

None of the above

Why is the D-MOSFET ideal as a preamplifier? (A)

It can be mid·load line when 0 Vis applied

(B)

It bas a high input impedance

(C)

It has low noise properties

(D)

All the above ll

141

70.

71.

Which of the following circuits is connected in an open-loop mode?

(A)

Comparator

(B)

Inverting amplifier

(C)

Non-inverting amplifier

(D)

All the above

What is the lower frequency limit of an op-amp? (A)

72.

73.

20Hz

(B)

76.

76.

141

(C)

DC

(D)

7.36 Hz

The loop in a closed-loop op-amp circuit provides (A)

Positive

(B)

Negative

(C)

Degenerative

(D)

Both (A) and (B)

In the below circuit, the required value ofRt, is,

(A) 97 K 74.

6Hz

Super-~

(B)

10 K

(D) 120 K

(C)

117 K

Darlington configuration

transistor is a

(A)

Cascade configuration

(B)

(C)

Matched-pair


For an ideal noise free transistor amplifier, the noise factor is

(A)

zero

(B)

1 dB

(C)

depends upon circuit parameters

(D)

zero dB

A NAND circuit with positive logic will operate (A)

NOR with negative logic

(B)

AND with negative logic

(C)

OR with negative logic input

(D)

AND with negative logic input

12

77.

In full adder, there are (A)

Two binary number inputs and two outputs

(B)

Three binary digit inputs and two binary outputs

(C) Three binary digit inputs and three binary digit outputs

(D)

None of the above

78.

How many illegitimate states have a synchronous mod-6 counter? (B) 2 (C) 1 (D) 0 (A) 3

79.

An AND gate is a

80.

81.

(A)

Sequential circuit

(B)

Memory circuit

(C)

Relaxation circuit

(D)

Combinational circuit

LED

A device with slowest switching speed is (A)

LCD

(B)

(C)

Nixie tubes


The instrument with null output is (B)

{A)

Bourdon gage

(C)

A platform weighing scale

Manometer (D) Light meter

82.

A spurious signal that modifies the output of the instrument is called (B) Spurious output (A) Noise (D) Modulating signal (C) Either (A) or (B)

83.

In shunt type ohmmeter the maximum deflection point is marked

(A) 84.

85.

lOOKO

(B)

1 MO

(C)

10MO

(D)

lhfinite

Normally absolute encoder are used for (A)

continuous speed

(B)

27t revolutions

(C)

one revolution

(D)

both (A) and (B)

Multirange ammeter uses

(A)

Universalshunt

(B)

Series shunt

(C)

Parallel shunt

(D)

All of the above

13

141

86.

An LED require a power of (A)

87.

88.

89.

91.

92.

93.

141

(B)

20 i!W

(C)

20 mW

(D) 20 W

The phenomena of creeping occurs in (A)

Ammeters

(B)

Voltmeters

(C)

Wattmeters

(D)

Watt-hour meters

Half effect transducer are used for measuring (A)

Magnetic field

(B)

Current

(C)

Electrical field

(D)

Pressure

Loss of charge method is utilized for measurement of (A)

90.

20 nW

high L

(B)

(C)

highR

JowL

(D)

low R

The range of a d.c. millimeter can be extended by utilizing a (A)

Series high resistance

(B)

Series low resistance

(C)

Shunt of high resistance

(D)

Shunt of low resistance

- - - - - - are very popular in switched mode power supplies. (A)

Power MOSFET

(B) :S.JT

(C)

IGBT

(D)

None of the above

In IGBT, the tine between the instants of forward blocking to forward on-state is called (A)

Delay time

(B)

Rise time

(C)

Tum-on time

(D)

Turn-off time

For the operation of Zener diode as a voltage regulator (A)

it must he reverse biased with a voltage greater its breakdown

(B)

a series re$ister

(C)

necessary to limit the reverse current

(D)

all the above

14

94.

The device having high voltage-blocking capability {A)

95.

97.

(B)

{C)

RCT

MCT

(D) ASCR

In resistance firing circuit of SCR, a can be controlled upto

(A) 96.

FCT

45°

(B)

so•

(C)

135°

(D)

180"

Me Murray inverter uses {A)

Voltage cotnmutation

(B)

Current commutation

{C)

Natural commutation

(D)

Input commutation

A three phase voltage source inverter operates with 180° mode, whose input DC voltage is kept V5 • What would be the output fundamental rms voltage per phase if the load connected to the inverter is star connected?

v<21a> vs 98.

99.

Chopper control for DC motor provides variation in {A)

Input voltage

(B)

Frequency

(C)

Current

(D)

None of the above

Identify the constant flux operated variable speed drive (A)

FJf controlled I.M. drive

(B)

Slip power recovery drive

(C)

(A) and (B)

(D)

AC voltage controlled l.M. drive

100. Duty cycle in a chopper circuit with switching frequency 100 Hz and Ton time as 2 ms (A)

0.2

{B)

0.4

(C)

0.8

(D)

None of the above

15

141

ENTRANCE EXAl\UNATION FOR ISSION. MAY 2011. Ph.D . (ELECTRICAL AND ELECTRONICS ENGINEERING)

COURSE CODE: 141

• Number :

L'-----...J Signaturt af the fnvrgrlator (w•th date)

COURSE CODE 141 Ttme : 2 Hours

Max . 400 Marks

Instructions to Candidates: 1.

,

'

2.

Write your Number within the box provided on the top of this page and fill in the page 1 of the answer sheet using pen. Do not write yow· name anywhere in this booklet or answer sheet. V10lation of thts entails disqualification.

3

Read each question carefully and shade the relevant answer (A) or (B) or (C) or (D) in the relevant box of the ANSWER SHEET using HB pencil

4.

Avoid blind guessing. A wrong answer wtll fetch you -1 mark and the correct answer will fetch 4 marks.

5

Do not wnte anything in the question paper. Use the white sheets attached at the end for rough works.

6.

Do not open the question paper until the stBI·t signal is given.

7.


8.


9.


t.

f (t) is given

The Laplace transform of a function

1

by F (s) = f

2

\52 + 1)

•

The value of

•

the integral

Jf (t)e·tt dt

is

0

(A)

2.

o

(B}

0.04

4

(0)

"'

A real valued periodic function f(t) has period T. The Fourier series expansion

contains no of frequency w the function f

3.

(C)

= 2n: (K/T), K = 1, 2,···

and no sine . Then

(t) satisfies

(A)

f (t) = - f (t - T)

CB>

(C)

f (t) = - f (t- T/2)

en>

r (t) = r (t - r) r (e)= r (t- r;2)

For the differential equation, dy + 5y = 0, with f (0) d;x

= 1,

the general solution is of

the form (A)

4.

5.

e"

Newton Raphson iterative formula for the solution of x~ - 1

= + (x~ -1)/2x;

(A,)

X;+ 1

(C)

x;., = + (2x? - t)/2x,

Lt

....... .., (A)

7.

X

I d

= 2 2x,

x,2 + }

(B)

0

(C)

-1

X=

1

(B)

-

X

3

"'

+1

x) is at (C)

:c = 3/2

(D)

(D)

A bag contains 8 white balls and 6 red balls. The probability of drawing two balls of the sa rue colour is (A)

141

(D)

'

(x~ + l)/2x,

X

The minimum point of the function ( ~A)

x;., = +

is

sin..:. - tsequ alto

2

6.

(B)

=0

21 91

(B)

13

(C)

.. 1~

2

43 91

(0}

41 91

8

The rank of the matrix A, is given by A

(A)

9.

10.

The matrix A

1

[M8 =

sine si~ 8 cos 8 0

[" ~] (C)

2

(D)

3

tD)

z -1 z

:J"

(A)

orthogonal

(B)

non -orthogoual

(C)

singular

(0)

non-singular

The Z-trausform of a discrete unit step function is given by (Aj

11.

(B)

0

~

0 4 2 3 ' 1 0 0 4 0 3

z

z+1

(B)

z +1

(C)

z

z

z -1

An overhead line conductor is composed of three identical strands each of radius 'r' and arranged as shown in figure. The self GND of the conductor is given by

'

(A)

12.

2
(C)

2 113

r

(D)

2 81 !1 r

R 2

(B)

R

(C)

2R

(D)

For an overhead transmission line, the resistance per phase is R and reactance per phase is X. The ultimate power transmitted will be maximum when (A!

14.

(B)

The insulation resistance of a s1ngle core of certrun length is R ohms, the insulation resistance of the same cable, when the length is doubled will be (A)

13.

2v• · r

X= R

(B)

X= ../2 R

(C)

X= .f3R

(D)

X= 2R

Use of bundled conductors is 0/H line (A)

reduces the reactance of the line and increases the radio interference

(B)

reduces both the reactance and inter ference

(C)

increases the reactance of the line and reduces the radio interference

(0)

increases both the inductance and interference 3

141

15,

16.

In corona calculations, air density factor is used, which is (A)

directly proportional to temperature and atmospheric pressure

(B)

inversely proportional to temperature and pressure

(C)

directly proportional to temperature and inversely proportional to pressure

(D)

directly proportional to pressure and inversely proportional to temperature

Match List 1 and List 2 and select the correct answer : List 1

List 2

1.

Mho relay

(a}

Generator protection

2.

Buchhalz relay

(b)

Motor protection

3,

Differen tial relay

(c)

Transformer protection

4.

Thermal re lay

(d)

Line protection

(A)

1 - {b), 2 - (a),

(B)

1- (c), 2- (d), 3- (a), 4 -(b)

a- (d),

4 - (c)

(C) 1- (d), 2- (b), 3 - (a), 4- (c) (D)

17.

A 3 phase, 50 Hz, 4·pole, 20 MVA, 11 kValternator has the inertia constant of9 sec If the input minus losses is 20 Mw and the output is 16 Mw, then the acceleration in abc. degree/sec2 is (A)

18.

141

1- (d), 2 - (c), 3- (a), 4 - (b)

100

(B)

(C)

200

300

(D)

400

Voltage-time characteristics of a lightening arrestor and a transformer are shown in figure for p roper insu lation coordination, the sui tab le characteristic is

(A>

(B)

(C)

(D)

4

-.

19.

Current chopping may occur in the following circuit breaker : (A)

20.

Bulk oil

(B)

22.

23.

24.

(C)

Minimum oil

(C)

,/LC

(0)

SF6

The surge impedance of a line is given by

(Bl 21.

Air blast.

~C/L

A system is said to be linear (A)

if it obeys the ma:llimum power transfer principle

(B)

if it obeys the principle of super position

(C)

if its output remains constant

(D)

if it obeys the law of gravity

A linear time invariant system is said to be stable if (A)

its impulse response is absolutely integrable

(B)

it is casual

(CJ

the output is bounded for any input

(D)

the output is time invariant

A white noise is that signa] whose spectrum (A)

extends over infinite range

(B)

has spectral densjty varying as 1/t

(C)

has flat spectral density

(D)

has limited number of frequency components

The poles and zeros of a transfer function, are the frequencies at which the function value (A)

re11ches in.fi.nhy al poles and zero at zeros

(B)

reaches zero at poles and infinity at zeros

(Cl

reaches zero at both poles and zeros

(D)

reaches infinity at both poles and zeros 5

141

25.

26.

The Laplace transform of the function shown m figure is given by

(AI

(B)

-1

(t -e-· -e -t.)

(Cl

(0)

-1

(t -e-· -se-•·)

s•

s•

The state and output equatiOns of a control system are given by

X = AX + BU and Y = CX • DU. The transfer function relatmg the output ·yo to the input 'll is given by

27.

(A)

C (SI - A}" 1 D

(B)

C (Sl- A} · B

(C)

C (SI - A)"' B

(D)

CB (SI- At' - D

D

For the signal flow graph shown in figure the number of forward paths and the number of pairs of two non touching loops, are given by )

(A)

28.

~

3, 1

(B)

~ (C)

4, 0

;)!

(0)

3, 2

3,0

The uruL sLep input response of a certain control system is C (I)= 0 5 (1- r· 11 ). ft is cascaded with another system whose impulse response is given by h (1) = e-• The transfer function of the cascaded system is

(A) (C)

141

1 6

(B)

(5+ 2) 1

(D)

(s+ 2) 6

1

(s+l)(s-2)

s

•

29,

The Nyquist plot of a open loop stable control system is shown in figure. The stability of the system is inferred as

(A)

(C)

30,

unstable critically stable

(B)

{D)

stable stability cannot be ascertained

Tho: number of roots of the equation 2s• + 6 3 + 3s1 + 5s + 7 =0 that lie on the right half of's' plane is 0 00 1 ~ 2 ~ 3

w

31.

For the circuit showp in figure the Thevenin equivalent circuit at the terminals, AB 1s

..-----,----_,. A-

•

I ~.4-

32.

t

(A)

./2 {1 + j2) 0

(B)

2j 45' V, (1 - j2) 0

(C)

2j4.s·, (1 + ji) n

(D)

.f2j45' V, (1 + Jl) 0

For the circuit shown in figure, the currents through respectively

Ra

and the voltage somce 'V are

(/t (A)

33.

1, 4

(B)

5, 1

(C)

5, 2

{D)

5, 4

A 400 V, 50 Hz, three phase source, supplies a star connected load rated 12../3 KVA, 0.& pf lag. To improve the power factor to unity, the KVAR rating for the capacitor banks is (A) 28.78 (B) 21.30 (C) 16.60 {D) 12.41 7

141

34.

When a unit impulse voltage is applied to an inductor of 1 H, the energy supplied by the source is (A)

35.

1J

(B)

0J

(C)

0.5 J

(D)

., J

(D)

2 RC 3

The time constant for the circuit shown in figure is

r

~

V-

(A)

36.

2 RC

(B)

(C)

3 RC

RC

2

The current waveform shown in figure is applied to a 10

n resistor. Power dissipated

in the resistor is

1 (A)

37.

7.29

w

(B)

52.0 w

(C)

135 W

(D)

270 w

An electrical network has n·nodes and b·branches. Then the number ofloop equations

required t.o solve the network, is given by (A)

38.

(B)

n- b + 1

b- n.,.. J

(C)

b+ n +1

(D)

b- (I -1

The unit impulse response of a circuit is given by C (t) "' - 4~-• + 6e-". Then the unit step response of the system will bf' (A)

39.

The Z-transform of the function ((nT) = a"T is (A)

141

- 3e-2' + 4·e_, + 1

z

(8)

z

(C)

8

z

(D)

z

•

40

The Z 11 -parameter for the circuit shown m figure is )

-----L-----z-1

I ~I (Al 41.

42.

43.

~4 .

(A)

1.~

(C)

/~

30

(C)

(D)

20

10

IL

(B)

lh < IL

> }L

(D)

I. has no relation to 1L

The turn on time CJf an SCR can be reduced by using (A)

a triangular pulse

(B)

a tnpezoidal pulse

(C)

a rectangular pulse of high amplitude and low width

(D)

a rectangular pulse of low amplitude and high width

Choose the correct statement : (A)

Both MOSFET and BJT are voltage controlled devtces

\B)

Doth MOSFET and BJT are cul'l'ent controlled devices

(C)

~OSFET is

(D)

MOSFET is voltage controlled and BJT is current controlled

current controlled and BJT is voltage controUed

In a BJT. the relationship between a and a

P=-l+a

(B)

a

P= a --l

p

is given by

(C)

a=_!!_ p -1

(D)

A:n SCR oan withstand a maximum juottiun temperature of 120•c, at an umb1ent nf 45°C. Thermal resistance of the SCR from junction to ambient is 1.5•Ctwatt. The mllXlJl'lum internal power dissipation in watts is lA)

46.

(Bl

ln a thyristor, the holding currenl /• and latching current I c arE> relalecl a,;

(A)

45.

60

80

(B)

60

(C)

50

(D)

30

The device wruch is smaller in size and cheaper, that can be used for high frequency applications, is given by (A)

SCR

{D)

TRlAC

(C)

9

GTO

(0)

MOSFET

141

47.

Most reliable, efficient and commonly employed method for triggering of SCR's is (A)

d v/ dt trigger ing

(B)

Gate triggering

(C)

forward voltage triggering

(D)

light triggering

In a single phase full converter, the peak and average values of output voltages are 325 V and 133 V respectively. Then the firing angle will be

48.

(A)

(B)

so•

(C)

(A)

3750 W

(B)

3250 W

(C)

2500W

1760 w

(D)

List 2 - PropPrties

1.

TRIAC

(a)

Voltage driven device

2.

MOSFET

(b)

Five layer device

3.

GTO

(c)

Switching speed of 100khz

4.

1 GBT

(cl)

High gate drive losses

(A)

1 - (b), 2- (a), 3- (d), 4-(c)

(B)

1 - (a), 2 - (d), 3 - (d), 4 - (c)

I

C) 1-(d),

(.D)

2 - (c), 3 - (a), · l - (b)

1 - (c), 2 - (d), 3 - (b), 4- (d)

For a 3 phase, six pulse, diode rectifier, the average output voltage 1n of the maximum supply line voltage is given by

(C)

(B)

(A)

52.

140°

(D)

);iatch List 1 and List 2 and give the correct answer using the codes given below . List 1- Devices

51.

130•

A step down chopper bas a load resis tance of 10 ohms, input voltage of 250 V. a chopping freq uency of 1 KHZ and a duty cycle of 40%. Then the output power will be

49.

50.

4o•

(D)

3../3 v 1C

..

In the circuit shown in figure, the maximum value of the current through the diode is

• (A)

Hl

~4

A

(B)

36 A

(CJ 10

48A

(D)

60 A

53.

For the inverter shown in fi~r-ue the voltage waveforms IIJo and v20 are given along side. What is the rms voltage between terminal! and 2 i.e. u12 ? ~

+

1t

J (A)

54 ~

V,a

Ji1C

~f'

(D)

(C)

(B)

P- r

a Vs·-

.[;

Tu a single pulse modulation of PWM inverter, the third harmonic in the output voltage may be eliminated, if the pulse width is equal to

(A) 35.

-

30•

(B)

60°

(C)

120•

(D)

150°

The load and motor torque characteristics are given below. The typical example for tLDstable system is

(A)

(B)

(D)

56.

F'or low speed, high power reversible drive, the most suitable drive

cyclo·converter fed a.c. drive

(B)

current source inverter fed ac drive

(C)

voltage source inverter fed ac drive

(D)

a.c. voltage controller fed induction motor. 11

141

57.

58.

In a power controller, fLring angle a, extinction angle related by

p and conduction angle, r are

(A)

a: P- r

(B)

{J:y-a

(C)

r: P- a

(D)

a - p +r :

o

--r .

For the four quadrant d.c. chopper shown in figure, for reverse motoring, which SCR is to be operated?

(D)

59.

If the half cycle surge current rating of an SCR is 6000 t at 50 Hz supply, then the one cycle surge current rating will be (A)

60.

62.

(CJ

4242 A

6000A

(D)

.../2 X

6000 t

(BJ

45•

so•

(C)

(D)

75•

go•

The equation that represents the Gauss law in a homogeneous isotropic medium is (A)

f D · ds = ff p dA

(B)

v

(C)

v ·J

(D)

V . E: p/e

- p :

o

X

H = D

A metal sphere 1m radius having a surfs.ce charge density of 10 C/m 2, is enclosed in a cube of 10m side. The total outward electric displacement in coulombs, normal to the surfs.ce of the cube is (A)

141

(B)

3000 A

In a dual converter operation, the circulating current will be zero if the firing angle of the first converter is (A)

61.

T,

40 tt

(B)

(D)

10

12

2

63.

Two point charges + Q and - Q are placed at the two opposite comers of a square. If the potential at the other corner is l V, then the potential at t.he centre of the square is (A)

64.

66

0.015 J

(B)

70.

(D)

J2v

0.15 J

(C)

0.5 J

(D)

1.15J

linearly polatized

(B)

right circularly polarized

(Cl

left circularly polarized

(D)

elliptically polarized

The total flux coming out of a cylinder placed in a uniform magnetic field is

1 Wb

2 Wb

(D)

5 Wb

'he meter constant of a single phase 240 V, induction type energy meter is -!00 revolutions per kwh. When a current of 10 A at 0.8 pf lng, flows, the speed of the meter disc will bt• 12.8 rpm

(B)

16.02 rpm

(C)

18.2 rpm

(D)

26.1 rpm

For the bridge shown in figure the reading of the high Impedance voltmeter is

(A)

b~

v

(A)

lA)

tH<.

1

A plane electromagnetic wave travelling along + Z-direction has its electric field E, = 2 cost and E1 = cos(t + 9 i). The wave is

(BJ 67.

(<.:)

../2

The energy stored in the magnetic field of a solenoid 30 em long and 3.0 em diameter, wound with 100 tllrns of wire, carrying a current of 10 A is (A)

65.

_I_\'

0

0

(B)

6.66\

(C)

11.2 \'

lD)

3.33 V

Wheatstone bridge method is ideally suited for the measurement of resistances in the range of \A\

0.001 to 1 0 ohm

(B)

0.1 to 100 ohms

((')

100 t.:> 10 k·ohm3

(D)

100 K to 10M-ohms

A 2000 n, voltmeter consum es 2.0 mw, when connected to a d.c. source. Tf a 4000 vo ltmeter is connected to the same circuit, the power consumption will be (AI

4.0 rnw

(B)

l.Omw

(C)

13

2.0 mw

(D)

u.

0.5 m"

141

71.

The Q factor of a coil at a resonant frequency of 1.5 MHz of an RLC series circuit is 150. Then the bandwidth is (A)

~.,

'-·

(B)

1.06 MHz

(C)

10kHz

(D)

0.001 MHt

A 150 V moving iron voltmeter with class 1 accuracy reads 75 V, when used in ... circuit under standard conditions. The maximum possible percentage error in the reading is

(A)

73.

225 MHt

0.5

(B)

(C)

1.0

2.0

(D)

4.0

Four ammeters have the full scale value and % accuracy as give.n below : M 1 -+ 20 ± 0.1,

M 2 -+ 10 ± 0.2

M 3 -+5 ± 0.5,

M 4 -+ 1 ± 1.0

A current of 1 A is to be measured with minimum error in the reading. The meter to be selected is (A)

74.

75.

(D)

(A)

VTVM

(B)

CRO

(C)

MI voltmeter

(D)

Digital multimeter

How many base circuits does a dual trace CRO, bas? 1

(B)

(C)

2

The states of tbe diodes shown in figure are l.J--

n, (A)

(B)

(C) (D)

141

M,

To measure n signal of 10mVat 75 MHz the meter to be used is

(A)

76.

M,

DJ

ON OFF OFF ON ON OFF OFF ON

DJ

OFF OFF ON ON 14

3

(D)

4

77.

For the damper circuit shown in figure the waveform of voltage at point P, for sinusoidal input voltage will be

(A)

78.

,[\U.

fVll"

(B)

~:;tlLJf

~'fTE K

(D)

~t:J¥

The common emitter forward current given for the transistor shown in figure is 100. Then thtt transistor operates in +-it> I/

79.

(A)

saturation region

(8)

cut off region

rC}

reverse active region

(D)

forward active region

What is the power dissipated m the transistor of the voltage regulator shown in iigure? -

jkJl-

fDV

l!.v

i

/IJ..A-

+ (AI

OJ'i w

(B)

2.4

(C)

IV

15

4.2

w

(D)

5.4 w

141

80.

In the XOR gate circuit shown in figure A, B. C, D are inputs and Y is the output. Then nature of the sum, s and output Y is

~:---7.t::.--

;:.---h

81.

(A)

sis always either zero or odd

(8)

s is always either zero or even

(C)

s

(D)

s = 1 only if the sum of the input is odd

=l, only if the sum of inputs is even

For what range of triggering angle (a) the output voltage is not controllable for the circuit shown in figure.

82.

(A)

0 < 45'

(B)

45' < a < 135'

(C)

90' < a < 180'

(D)

135' < a < 180'

For the circuit shown in figure R, : R, and R3 = R 4 • Then the circuit acts as a

~,

141

(A)

all filter

{B)

band ftlter

(C)

high fllter

(D)

low filter

16

83.

An amplifier bas a overall current gain of 100 and an input resistance of 10 kn If the load resistance is 1 kn, the overall voltage gain will be (A)

84

!lti.

•

bS.

89

(C)

(D)

20

10' 1

(BJ

10-3

(C)

Hl'

For the flip-flop circuit shown in U){Urc the non stable state correspondB to

(r\l

y - 0, y

=0

(B)

X= 0, Y = 1

tC)

X- 1 Y

=0

(D)

X= t, Y

=1

A 300 K VA transformer has 95% effirtenry at full load, 0.8 pflag and 96% eflici£'ncy al hulf load, upf. Then the ma"'"'""'' efficiency n~ upf will be (A!

...,7,

10

An op-amp has a common mode gain of 0.01 and a differential mode gain of lOa. Then the common mode rejection rntio will be (A)

85.

(B)

6

1-!5.1%

(B)

(D)

96.2%

98.1%

In a transformer, zero voltage regulation at full load is

tAl

not possible

(B)

po~sible

(C)

poss1ble at leadtng pfload

(0)

possible at logging pf load

at upf load

A d.c. motor, which can provide- zero ~peed regulation at full load, without any •·ontroller is a (A)

Sleries motor

(B)

shunt motor

\C)

cumulatnre compound motor

(D)

differential compound motor

The total reactance and suceptance of a lossless EHV line of 50 Hz are 0.045 and 1 2 p.u

respectwely. The velocity of wave propagation 1s 3 "10) KM/sec.

The

npproXJmate length of the line will be

IAI

122 km

(B)

185 km

222km

(D)

27:.! km

141

90.

A 3 phase cage induction motor has a starting current of seven times the full current. The full load slip is 5%. A star-delta starter is used to start the motor. The p.u. starting torque will be (A)

91.

0.607

{B)

0.816

(C)

1.225

(D)

1.816

The characteristic equation of a 3 x 3 matrix, Pis given by a (,t); l 3 + A2 + 2 A+ 1 : 0. If J is the identity matrix, then the inverse of matrix. P is given by

92.

93.

(A)

(P 2 + P + 21)

(B)

(P 2 + P + I}

(C)

-

(P 2 + P+ 1)

(D)

- (P 2 + P + 2/)

ln a stepper motor, the detent torque means (A)

minimum of the static t~rque, when excited

(B)

max.imum of the static torque, when excited

(C)

minimum of the static torque, when not excited

(D)

ma.ximurn of the static torque, when not excited

A 400 V, 50 Hz, 22.5 kW. 3 phase induction motor draws a current of 50 A of 0.8 pf lag. The stator copper losses are 1.5 kW and that of rotor 900 W. The core losses

ar~

1.2 kW and windage and friction losses are 1.05 kW. Then the air gap power of the motor will be !A)

94.

23 kW

(B)

24 kW

(C)

25 kW

(D)

26 kW

A 3 phase, 440· V. 50 Hz, 4 pole, step ring induction motor is fed from the rotor side through an auto transformer and the stator is connected to a variable res1stance . The motor runs at 1410 rpm. The speed of rotation of the stator magnetic flux with respect to the rotor will be (A)

90 rpm in the direction of rotation

(B)

90 rpm in the opposite direction of rotation

(C)

1500 rpm in the direction of rotation

(D) 1500 rpm in the opposite direction of rotation 141

18

95.

9u.

The speed-torque characteristics of a 3 phase cage induction motor and the load are shown in fig. Which is the correct description of the equilibnum point.s A and B?

(A)

A is stable of B is unstable

(B)

A is unstable of B is stable

(C)

Both A and B are stable

(D)

Both A and B are unstable

A single phase iron core transformer has bot.h the horizontal cores of cross sectional

nrea l 0 cm 2 aud the two vertical cores of 20 em'. The two windings are on the vertical

cones. The mutual inductance is L. If the two windings are wound on the horizontal core arms. the mutual inductance will become (Al

i! L

(B)

(C)

L

, ~;

L 2

(D)

L 4

A 220 V, 50 H, single phase motor with Mt M. as the main stator winding and At A. as

the auxiliary winding with flux directions, is shown in Fig. The direction of rotation of the rotor will be

(A)

clockwiSe

IB)

anticlockwtse

!C)

no rotation possible

(DI

rotates momentarily and comes to a stop

19

141

98.

99.

For the ideal transformer shown in Fig. The input source current is 10 sin 314t. The magnetizing inductance is 400/tr mH. What is the load voltage?

(A)

400/ J2

(B)

320/./2

(C)

240/./2

(D)

160/J2

An 8085 micro processor based system uses a 4 KXB bit RAM, whose starting address is AAOOH. The address of the last byte in this RAM will be (A)

OFFFH

(B)

lOOOH

(C)

B9FFH

(D)

BAOOH

lOO. A 3300 V, 3 phase star connected synchr·onous motor bas a synchronous impedance of {0.4 + j 5) ohms per phase. For an excitation emf of 4000 V and motor input of 1000 kW, the line current will be

141

(A)

184.5 A

(B)

144.5 A

(C)

154.5 A

(D)

1646 A

20

ENTRANCE EXAMINATION FOR ISSION, MAY 2013. Ph.D. ELECTRICAL AND ELECTRONICS ENGINEERING COURSE CODE: 141 Number

:j,_--"'-----' Signature of the Invigilator (with date)

COURSE CODE: 141 Time : 2 Hours ·

Max : 400 Marks



2.


3.

Read each question carefully and shade the relevant answer (A) or (B) or (C) or (D) in the relevant box of the ANSWER SHEET using HB nencil.

4.


5.


6.


7.


8.


9.


1.

The range of wind speed suitable for wind power generator is (A) 0 to 5 mls (B) 5 to 25 m Is (C) 25 mls to 50 mls (D) 50 mls to 75 mls

2.

A wind turbine extracts maximum power from wind, when the downstream wind

speed reduces to (A) one-third that of upstream wind (C) two-third that of upstream wind

·

half that of upstream wind (D) zero

(B)

3.

If the speed of a wind stream remains unchanged while ing through the rotor (A) a large power will be generated (B) zero power will be generated (C) the flow is known as stalled flow (D) the speed of the rotor will be very high

4.

Grid - connected wind generators usually have maximum penetration of (A) 10 to 20% (B) 20 to 30 % (C) 30 to 40 % (D) 40 to 50 %

5.

Stall regulation is used with turbines (A) having diameters less than 25 m (C) having rotors oflarge solidity

having diameters more than 25m (D) having rotors with pitch control (B)

6.

When VAR flow in a circuit is increased, losses in the circuit are (A) reduced (B) not changed (C) reduced if the circuit is inductive and increased if the circuit is capacitive (D) increased

7.

The equality constraint, when the transmission line losses are considered is given by, (A)

•

LPa1 -Pu... =0

•

LPa1 -P0 =0

(D)

LPai =P0 +Pr.o..

141

,

"

i•l

1•1

8.

.

LPa1 -P0 =P"",+Pa

1-1

(C)

•

(B)

=

The fuel cost of a l,lllit is given by C 1.5 + 20 Po +0.1 l'2o· where Po is the unit output in MW. The incremental fuel cost at an output of 100 MW is (A) 60 Rs. I MWh (B) 40 Rs. I MWh (C) 100 Rs. IMWh (D) 20 Rs. I MWh

2

9.

For economic schedule of a load of 180 MW, the plant outputs p, and P2 are given by (A) p, 100 MW; P2 80 MW (B) p, 90 MW; P2 90 MW (C) p, = 80 MW; P2 = 100 MW (D) p, = 120 MW; P2 = 60 MW

=

=

=

=

10.

To determine the units that should operate for a particular load is the problem of (A)_ Unit commitment (B) Optimal load scheduling (C) Economic dispatch (D) Optimal power flow

11.

In the priority list method, the units are arranged to commit the load demand in the order of (A) Ascending costs of units (B) Descending costs of units (C) Either (A) or (B) (D) Independent of costs of units

12.

In the optimization problem of a hydro-thermal system, which of the following are chosen as independent variables? (A) Water storages in all sub-intervals except one sub-interval (B) Water inflows in all sub-intervals. except one sub-interval (C) Water discharges in all su) rel="nofollow">-intervals except one sub-interval (D) Hydro and thermal generations, water storages at all intervals, and water discharge at one sub-interval

.

13.

The basic function of LFC is (A) To maintain frequency for variations in real-power demand (B) To maintain voltage for variations in real-power generation (C) To maintain both voltage and frequency for variations in real-power demand (D) To maintain both voltage and frequency for variations in real-power generation

14.

The primary control loop in generator control is (A) Linkage mechanism (B) Fly-ball speed governor (C) Speed changer (D) Hydraulic amplifier

15.

Damping of frequency oscillations for a two-area system is more with (A) Low-R (B) R = oo (C) High R (D) Independent ofR

16.

For synchronous condensers, the p.f. improvement apparatus should be located at (A) Sending end (B) Receiving end (C) Location is n9t important (D) Middle of the line 3

141

17.

In synchronous condensers, leadingVARs ar~ produced by (A) Increasing field current (B) Decreasing field current (C) Increasing speed of the machine (D) Decreasing speed of the machine

18.

VARs always flow from (A) Points of higher angle to points of lower angle (B) Points of lower angle to points of higher angle (C) Points of higher voltage to points of lower voltage (D) Points of lower voltage to points of higher voltage

19.

In contingency ranking, the severest fault will be ranked (A) 1 (B) Last (C) Will depend on the type of fault (D) Will depend on the duration of fault

20.

The smaller the lagging reactive power drawn by a circuit, its p.f. will be (A) Better (B) Poorer (C) Unity (D) Zero

21.

The turn-on time of SCR wilh inductive load is 30 JLS. The pulse train frequency is 3.0 1 kHz with mark I space ratio of - then the SCR will 10 (A) Turn-on (B) Not turn-on (C) Turn-on if inductance is removed (D) Turn-on if pulse frequency is increased to two times.

22.

The main reason for connecting a pulse transformer at the output stage of a thyristor triggering circuit is to (A) Amplify the power of triggering pulse (B) Provide electrical isolation (C) Reduce the turn-on time of the thyristor (D) Avoid spurious triggering of thyristor due to noise

23.

A three phase semi-converter feeds the armature of a separately exited de motor supplying a non zero torque. For steady state operation the motor, armature current is found to drop to zero at certain instances of time. At such instances the voltage assumes a value which is (A) Equal to the instantaneous value of the ac phase voltage (B) Equal to the instantaneous value of the motor back e.m.f (C). Arbitrary (D) Zero

141

4

;_,.

24.

For very high and ultra high frequency applications, which of the following is preferred? (A) SIT (B) IGBT (C) MOSFET (D) BJT

25.

An SMPS circuit operating at 20 kHz to 100 kHz range uses which of the following elements (A) Thyristor (B) TRIAC (C) UJT (D) MOSFET

26.

The converter that can operate in both 3-phase ~nd 6-phase is (A) 6-phase, full converter (B) 6-phase, semi converter (C) 3-phase, full converter (D) 3-phase, semi oonverter

27.

If a (A) (B) (C)

28.

A thyristorised, three-phase, fully controlled converter feeds a de load that draws a constant current. Then input ac line current to the converter has (A) An rms value equal to the de load current (B) An average value equal to the de load current (C) A peak value equal to de load current (D) A fundamental frequency component whose r.m.s value is equal to de load current

29.

In an AC motor control, the ratio of voltage to frequency is maintained constant in order to (A) Make maximum use of magnetic circuit (B) Maximize the current drawn from the supply to provide torque (C) Make minimum use of magnetic circuit (D) None of the above

30.

If speed of a de shunt motor is increased above its rated speed, then its counter emf (A) increases (B) decreases (C) remains unchanged (D) first increases and then decreases

31.

The function of a de motor starter is to (A) start the de motor (C) increase the starting torque

single-phase voltage converter feeds an induction motor and heater then . In both the loads, fundamental and harmonics are useful In both the loads, only fundamental is useful In induction motor only fundamental is used and in heater, both fundamental and harmonics are useful (D) In induction motor both fundamental and harmonics are useful and in heater only fundamental is useful

(B)

limit the starting current (D) avoid dips in the supply voltage

5

141

32.

A synchronous motor, fed from infinite bus, is delivering half-full load. If an ip.crease in field current causes an increase= in the armature current, then the motor will (A) deliver reactive power and active power to the bus (B) absorb reactive power and active power to the bus (C) absorb reactive power from the bus and deliver active power to the bus (D) deliver reactive power to the bus and absorb active power from the bus

33.

A salient - pole synchronous motor 1s running with .normal excitation. If the excitation is reduced to zero (A) it becomes an idduction motor (B) it becomes a reluctance motor (C) it remains a synchronous motor (D) the motor would stop

34.

The torque -slip characteristics of a poly-phase induction motor becomes almost linear at small values of slip, because iil this range of slips, (A) the effective rotor-circuit resistance is very large compared to the rotor reactance (B) the rotor resistance is equal to the stator resistance (C) the rotor resistance is equal to the rotor reactance (D) the rotor reactance is equal to the stator reactance

35.

The most common application of 3- phas,e, induction generator can be in a (A) steam-power station (B) hydro-power station (C) wind-power station (D) nuclear -power station

36.

A signal is an energy signal if (A) (C)

37.

(D)

39.

=

(B)

=0

(D)

time-invariant system time varying, dynamic system linear, time varying, dynamic system linear, time-invariant, static system

The circular convolution of x(n) = {1,2,1} and h(n) = {2,1,2} is (A) {7,7,6} (B) {6,7,6} (C) {6,7,6,0}

If z(n) ( zr (A)

l X(z),

(C)

(D) {0,7,7,6}

then the initial value theorem states that x(O) =

Lt (z- 1) X (z)

(B)

~~•

141

E = D, P = finite E = imite, P = D

Y(n) = %(2n) is for a

(A) (B) (C)

38.

E= 0, P= 0 E finite, P

Lt X(z) z~l

LtX(z)

(D)

......

6

LtzX(z)

......

40.

The z,transform of a signal with X(s) = (1/s) is (A)

41.

42.

1

(B)

1-z-

1

1

(C)

1-z

recursive system

(B)

non- recursive system

(C)

causal system

(D)

non-causal system

"

Lx(n)el""

·-

(B)

LX(n)e1..,

(D)

"

"

LX(n)e-1""' n=O

256

(B)

1024

(C)

512

(D)

128

In the bilinear transformation, the relation between s and z is (A)

8

=

.!(1

+

z-1)

T 1-z-1

·

(C)

47.

-

Lx(n)e_1..,

The number of complex multiplications involved in the computation of 256-point DFI' by radix ·2 FFI' is (A)

46.

z 1-Z

The DTFT of a sequence x(n) is defined as X(D) =

n•O

45.

(D)

(A)

(C)

44.

1+Z

1

A system whose output y(n) at time n depends only on present and past input values is called a

(A)

43.

1

8=

~G~:~:)

(D)

Interpolation results in (A)

decrease in sampling rate

(B)

increase in sampling rate

(C)

no change in sampling rate

(D)

random change in sampling rate

Which of the following characteristics are true for a RISC processor? (A)

Smaller control unit

(B)

Small instruction set

(C)

Short program length

(D)

Less traffic between U and memory

Which of the following is an undesirable dynamic characteristic of an instrument? (A)

Reproducibility

(B)

Dead zone

(C)

Time lag

(D)

Static error

7

141

48.

Flapper nozzle is used in alan _ _ _ _ controller. (A) electronic (B) hydraulic (C) pneumatic

(D)

none of these

49.

The closed loop pole of a stable second order system could be (A) both real and positive (B) complex conjugate with positive real parts (C) both real and negative (D) one real positive and the other real negative

50.

Smoke density of the flue gas going out of the chimney is measured by a (A) polarograph (B) thermal conductivity meter (C) photo electric cell (D) chromatograph

51.

Which of the following controllers has the least maximum deviation? (A) P-controller (B) P-I controller (C) P-1-D controller (D) P-D controller

52.

The transfer function for a PID controller is (where, To is the derivative time) (A)

Kc(l+T1B+T0 )s

(B)

(C)

1 Kc(1+T;B+-- ) ToB

(D)

T;

is the integral (reset) time and

Kc(1+.l_+T0 B) ris

1 Kc(1+J_+--) 1';8 ToB

53.

Which of the following thermocouples can measure the maximum temperature ? • (A) Platinum-rhodium (B) Tungsten-molybdenum (C) Chromel-alumel (D) Iron-constantan

54.

In a closed loop system, the process to be controlled is an integrating process with transfer function ll2s. The controller proposed to be used in an integral controller with transfer function 1/TJB. When a step change in set point is applied to such a closed loop system, the controlled variable will exhibit (A) overdamped response (B) underdamped response (C) undamped response (D) unstable response

55.

The graph of an electrical network has N nodes and B branches. The number of links L, with respect to the choice of a tree, is given by (A) B-N+1 (B) B+N (C) N-B+1 (D) N-2B-1

141

8

56.

Which of the systems having the following transfer function is stable ? (A)

.·

57.

1 s 2 +2

(B)

1 s 2 -28+3

(C)

1 s 2 +28+2

(D)

e-20, 2

s +28-1

The transfer function for a first order process with time delay is eTds

(A) (C)

e-Td'

Ts+1

(B)

Ts+1

(D) · Tds

1

(Ts+1)(Tds+1)

Ts+1

58.

Which of the following is not a mechanical pressure sensing element? (A) Bellows (B) Diaphragm (C) Bourdon tube (D) U-tube

59.

Which of the following is ndt a differential pressure flc;>w meter? (A) Rotameter (B) Flow nozzle (C) Oriflcemeter · (D) Venturimeter

60.

Time constant is the (A) time taken by the controlled variable to reach 63.2"/o of its full change (B) same as transportation lag (C) same as dead time (D) time required by the measured variable to reach 63.2% of its ultimate change

61.

E.m.f. generated by thermocouples is of the order of (A) milli volts (B) micro volts (C) volts

(D)

62.

Response of a linear control system for a change in set point is called (A) frequency response (B) transient response (C) servo problem (D) regulator problem

63.

Mcleoid gauge is' used to measure the (A) point velocity (C) vacuum

64.

kilo volts

flow rate (D) pressure

(B)

When the damping co-efficient (;)is unity, the system is (A) (C)

Over damped Under damped

(B)

Critically damped (D) Highly fluctuating

9

141

65.

66.

Back· to- back HVDC is used to (A)

increase the transmission capability

(B)

decrease line-losses

(C)

provide stable interconnection

(D)

reduce voltage drop

If response of a control system is to be free of o~et and oscillation, the most suitable controller is (A) · (B)

67.

68.

69.

70.

proportional-derivative(PD)controller

(C)

proportional-integral (PI) controlier

(D)

proportional integral-derivative (PID) controller

An embedded microcontroller means

(A)

A microcontroller for the embedded systems

(B)

Microcontroller with embedded processor .

(C)

A microcontroller with external memories storing the embedded software

(D)

Single ~hip microcontroller -based embedded system

8257 is for DMA transfer (A)

from peripheral to RAM

(B)

from RAM to peripheral

(C)

between peripheral and RAM

(D)

between floppy disk controller and RAM

A DAC output uses a low filter (A)

for line noise filtering

(B)

to reduce the effect of sharp 1 to 0 transition and 0 to 1 transitions at the DAC input

(C)

to drive low frequency output

(D)

to drive de motor

Seven-segment LED display glows only vertical and middle segments only. The displayed character will be (A)

141

proportional controller

H

(B)

B

(C)

10

A

(D)

E

71.

72.

An optoisolator

(A)

insulates the port pins of MCU

(B)

insulates the inputs from the interfacing motors, power devices, coils and relays

(C)

insulates the input from an output

(D)

insulates the outputs fiom the power inputs

IEEE488 (GPIB) bus has (A)

73.

74.

75.

76.

77.

16 lines

(B)

(C)

24 lines

18linee

(D)

20 lines

Stepper motor moves one step angle when (A)

current is transferred from one coil to the neighboring coil

(B)

insulates the input

(C)

current is switched on in the neighboring coil

(D)

when the current is given

all the coils

Interfacing circuit for a thermocouple is used for measuring temperatures (A)

voltage developed is measured

(B)

current developed is measured

(C)

resistance is measured

(D)

resistance change is mea.sured by MCU

For a robot wrist, ---'--is used. (A) DC motor

(B)

Stepper motor

(C)

(D)

Induction motor

Servomotor

For industrial control (A)

An advanced EPA (Event Processor Array) structure, PWM, WFG and multi-channel on-chip,ADC feature

(B)

Input capture and out compare units

(C)

PoweriO

(D)

An advanced EPA (Event Processor Array) structure, PWM and multi-channel on-chip ADC feature are must

A servomotor control uses (A)

timers

(B)

out compare features

(C)

real time features

(D)

PWM outputs

11

141

78.

A multi-touch screen senses by tow touch finger gestures such as zoom in, zoom out and rotate using (A) touch-screen controller (B) touch-screen controller, driver and library (C) touch-screen controller and driver (D) multi-touch library

79.

Assembler is a tool to (A) develop and editing source file in assembly language and create list and object files, and object file is executable after linking /location (B) develop arid editing compiled file in assembly language and create object file, which is executable after linking /locating (C) assemble file in assembly language and create object file, which is executable after linkingllocating (D) assemble macros

80.

If the step angle of the VR stepper motor is very small, then the modes of excitation is called as · (A) Full step operation (B) 2 phase on mode (C) Half step operation (D) Micro stepping operation

81.

The position sensor used in PMBLDC motor is (A) LVDT (B) Tachogenerator (C) Strain Gauge (D) Position sensor

82.

The learning rate in Neural network is used to (A) calculate the final output (B) control the amount of weight adjustment (C) make convergence faster (D) control the degree of similarity

83.

The method of hip value assignments based on common intelligence of human is (A) Inference (B) Intuition (C) Rank Ordering (D) Inductive reasoning

.84.

The process of fuzzy quantity into a precise quantity in fuzzy system theory is (A) Fuzzification (B) hip value assignments (C) Defuzzification (D) Aggregation

85.

141

Which operation of genetic algorithm prevents the algorithm to be trapped in a local minimum? (A) Selection (B) Mutation (C) Cross over (D) Reproduction

12

l

--

'

t

86.

A 64-bit word consists of (A) 4 bytes (B)

8 bytes

(C)

10 bytes

(D) 12 bytes

87.

How many storage locations are available when a mell)ory device has 12 address lines? (A) 144 (B)_ 512 (C) 2048 (D) 4096

88.

FlFO is formed by an arrangement of (A) Diodes

{B)

Transistors

(C)

(D)

Shift s

I

89.

90.

MOS cells

What are the following sequence of steps taken in deg a fuzzy logic machine? (A)

Fuzzification -+ Rule evaluation -+ Defuzzification

(B)

Rule evaluation -+ Fuzzification -+ Defuzzification

(C)

Fuzzy Sets -+ Defuzzification -+ Rule evaluation

(D)

Defuzzification -+ Rule evaluation -+ Fuzzification

During the analysis of Thevenin's and Norton's theorems (A) Voltage sources are short --i:ircuited and current sources are open - circuited (B) Voltage sources are open --i:ircuited and current sources are short - circuited (C) · Both voltage and current sources are short circuited (D)

Both voltage and current sources are open-circuited

91.

This filter transmits all frequencies lying between two-cut-off frequencies and attenuates all frequencies below lower cut-off frequency and upper cut off frequency. (A) low (B) high (C) band (D) None

92.

Which of the following is the source of non-linearity? (B) Saturation (A) Backlash in gears (D) Resistance (C) Both (A) and (B)

oa.

Th• (A) (C)

~··• mamx a

[-:•

!: ~'] (B) negative semi definite (D) negative definite

positive semi definite positive definite

13

141

94.

Addition of tubes to the transformer tank improves heat dissipation capacity because of (A) additional cooling surface (B) additional dissipation by radiation only (C) additional dissipation by convection only (D) additional dissipation by radiation and convection both

95.

Armature reaction in a synchronous motor at rated voltage and zero power factor (lead) is (A) magnetizing (B) cross - magnetizing (C) both magnetizing and cross - magnetizing (D) demagnetizing

96.

A 3-phase slip-ring induction motor is fed form the rotor side with stator winding short-circuited. The frequency of the currents in the short-circuited stator is (A) slip frequency (B) supply frequency (C) frequency corresponding to rotor speed (D) zero

97.

Which of the following IC is the timer? (A) 8255 (B) 8257

(C)

A wide range instrument should have (A) square -law scale (C) logarithmic scale

(B) linear scale (D) exponential scale

98.

99.

8259

(D)

8254

The current coil of a wattmeter is connected -to the CT of R phase. The potential coil is connected across Y and B phases. The wattmeter measures (A) active power in Y phase (B) reactive power in B phase (D) reactive power in R phase (C) active power in R phase

100. Demorgan's first theorem shows the equivalent of (A) OR gate and Exclusive OR gate (B) NOR gate and Bubbled gate (C) NOR gate and NAND gate (D) NAND gate and NOT gate

141

14

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