+-EI£c:r:RONICS -2012 ..
SET-A
3

1 cm of pure Germanium at 20°C contains about 4.2xl022 atoms, 2.5xl013 free electrons and 2.5xl013holes. 0.001% of Arsenic doping donates an extra 1017 free electrons in the same volume. The approximate number of holes in one cm 3 in the doped semiconductor under equilibrium condition is

a. 6.25xl09 b. 2.5xl09 C. 10.5xl09 . d. 1017


Measurement of Hall coefficient enables the determination of


Silicon is not suitable for fabrication of light emitting diodes because it is

a.
An indirect band gap semiconductor

b.
A direct band gap semiconductor

c.
A wide band gap semiconductor


d. A narrow band gap


The band gap of elements arranged in ascending order is:

a.
Diamond, Ge, Si

b.
Si, Ge, Diamond

c.
Ge, Si, Diamond

d.
Diamond, Si, Ge




The following statements are made for NMOS PMOS


a. Temperature coefficient and thermal conductivity
b. Mobility and concentration of charge carriers
c. Fermi level and forbidden energy gap
d. None of the above

1. The carrier mobility in NMOS is higher .2. PMOS require less area than NMOS
3.
NMOS. circuits are smaller than PMOS

4.
PMOS are faster in switching.


Qf these, the true statements are
a.
2and4only

b.
2and3only

c.
1and3only

d.
1,2 and 3 only



. . INDIAN SPACE RESEARCH ORGANISATION Page 1 of 19

... ."

The following statements are made for FETs
1.
In n-channel depletion mode MOS in the active region, the control voltage VGS is negative.

2.
NMOS in depletion mode is cut off for VGs=O

3.
NMOS in enhance mode is cut off for VGs=O

4.
There is no path between source and drain in the enhancement mode


Of these, the true statements are:
a. 1 and 2 only
b. lCll}d:30nly
c. 3 and 4 only
d. 3 and 4 only

Special handling precautions should be taken When working with MOS devices. The statement which is not true is
a. All test equipment should be grounded.
. ·b. MOS devices shpuld have their all leads shorted together during shipment and storage.
c.
Never remove or insert MOS devices with the power on.

d.
MOS devices do not require grounding straps used for CMOS.



If the input to the circuit of Figure is a sine wave, then the output will be

a.
Half wave rectified sine wave
. A full wave reCtified sine wave


c.
A square wave

d.
A triangular wave




A high gain OpAmp has Rf=10sQ Ri=103 Q. The correct statement is

a.
The non-inverting gain inverting gain are nearly same.

b.
The inverting gain is very much higher than non-inverting gain





.c. The higherthan invertinggail1 d..The inverting non-inverting gains are unrelated
INDIAN SPACE RESEARCH ORGANISATION Page 2 of 19


-----I-EtECTRONICS -2012 SET-A

For various types of oscillators, the correct statement is

a.
LC oscillators are more stable than crystal oscillators

b.
Crystal oscillators have highest Q

c.
Phase-shift oscillators have the widest range of frequency

d.
Wien bridge oscillator is used where a single frequency oscillator is required




For Butterworth Chebyshev filters, the correct statement is

a.
Butterworth response has a sharp cut-off

b.
Chebyshev response has a flat response in the pass band

c.
BuUerworth-l"'espoAsehas-ripples-inthe pass band

d.
Chebyshev response has ripples in the pass band




In a feedback series regulator circuit, the output voltage is regulated by controlling the

a.
Magnitude of the I/.P voltage

b.
Gain of the feedback transistor

c.
Voltage drop across the series pass transistor

d.
Reference voltage




In a fullwave rectifier circuit with centre tap transformer, if voltage between one end of secondary winding and centre tap is 300V peak, then PIV (peak inverse voltage) is


o.
a. 300V b. 150 V c. 600 V d. 900V
The rms value of the periodic waveform as shown in Figure is
A .


a. v3/2 A b. v2/3 A c. vl/3A d.. v2A
...--..

.

INDIAN SPACE RESEARCH ORGANISATION
Page3 of19.


.
..

10 10 -10
A
To infinity

The approximate equivalent resistance between terminals A and B for the following infinite ladder network comprising of 10 2 0 resistors is

d. 0.50
If the step response to the input step amplitude of 1 V is given by Voft}= Rc) the network can be represented by

a. b.

RC

e
c.
For a parallel RC circuit as shown in figure, R=200 &C=0.9 pF which is to be matched to 500 over a bandwidth,
R c
I

r

The circuit has to be matched over 6 GHz to 18 What r that cim be achieved:
a.0 b. 0.05 c. 0.1 .d.1
INDIANSPACE RESEARCH ORGANISATION
-Page 4 of19
SET-A
In this circuit, V is a sinusoid input with freq current i contains: 1


V AC rv Diode

Diode
a.OnlYI
.--All harmonics oft
c.
Only even harmonics ofI

d.
Only odd harmonics ofI


..
The effect of phase error of local oscillator on spectral components coherent detection of SSB Amplitude modulated signal is
a.
The frequency of demodulated signals varies with fixed amplitude

b.
Amplitude of demodulated signals varies with fixed frequency

c.
Both amplitude frequency vary

d.
The recovered signal has phase offset with fixed amplitude


The maximum transmission power efficiency of DSB-C Amplitude modulation is a.25% b.33.33% c.50% d.l00%
For identical total transmitted power, the ratio of SiN for wide band FM to
SiN of DSB-AM (with is (Given fm 15 KHz frequency.deviation KHz)
a.112.5
b.300
c.75
d.450

I­ INOlAN SPACE RESEARCH ORGANISATION Page 5 of 19


A signal 3cos(6000rrt)+4cos(7000rrt)+5cos(10000rrt) to be sampled. What is the minimum sampling. rate for band pass sampling for truth full representation:

a.
2000 Hz

b.
3000 Hz

c.
5000 Hz

d.
10000 Hz




Minimum number of bits required to represent maximum value of given analogue signal with 0.1% accuracy is:

a. 8 bits
b.9
bits

c.
10 bits

d.
12 bits




An Ideal power limited communication channel with additive white Gaussian noise is having 4 KHz band width and Signal to Noise ratio of 255. The channel capacity is:

a.
8 kilo bits /sec

b.
9.63 kilo bits Sec

c.
16 kilo bits Sec

d.
32 kilo bits Sec




An Ideal power limited communication channel with additive white Gaussian noise with 1 MHz band width and Signal to Noise ratio of 15 is transmitting the information at theoretical maximum rate. If the Signal to Noise ratio is reduced to how much bandwidth is required to maintain same rate:


a. 15/7 MHz
b.4/3 MHz

c.2
MHz

d.
None of these


INDIAN SPACE RESEARCH ORGANISATION Page 6 of19

SET-A

Following constellation diagram represents:

a.
16PSK

b.
16QAM

c.
16 APSK
d.AH6fab6ve





The information rate to be transmitted is 900 bits FEe is the symbol rate for QPSK modulation scheme is:

a.
225 symbols /sec

b.
450 symbols /sec





.
c.
600 symbols /sec

d.
675 symbols /sec


Electric displacement density 0 at any point on spherical surface of radius R
with a charge Q at the centre in a medium with dielectric constant e is: . a. Q/(4rr e R2}
b. Q/(4rr R2
E R)2
d. Q/(4rr R)2
Which of the following does not represent Maxwell's Equation:
a. pE. as =-fOB. aa
.. .
b. @D.aa p.aV
c.


d.
£PH. da= 0


.... .. .. ..•. .. . ......
INDlAF'-J SPACE RESEARCH ORGANISATION Page 7 of 19


For a homogeneous and isotropic medium with a charge density p dielectric constant the Poisson's equation for electrical potential V is


For a plane travelling EM wave, the -correct -equation for characteristic impedance Z for the medium with permittivity of £ and permeability of 11 is


a. VzV::E.
b. V £ E
c. v.v=E ·E
d. V.. v E ·E

a.

b.

c. Z
d. Z

plane wave propagating in the dielectric medium has an electric field given as Ex=EoCos (2.6xl010t -100z). The phase velocity of plane wave is
a.l0G m/sec
b.
2.6x108 m/sec

c.
3.0x108 °m/sec

d.
4.0x108 m/sec


A plane wave propagating in the dielectric medium has an electric field given as Ex=EoCos (3xl010t -100z). The dielectric constant of the medium is
a.l.33
b.i.00
c.1.01

.­
" INDIAN SPACE RESEARCH ORGANISATION Page 8 of 19

-----I-EEECTRONICS-2012
SET-A

A transmission line of 50 Q characteristic impedance terminated by a load impedance of 50-j50. The magnitude of reflection coefficient at the load is

a.
b. 43/5
d. None of above


The outer conductor diameter and the inner conductor diameter dimensions of a coaxial cable are made twiceto its original value. (Coaxial line is filled with dielectric material having dielectric constant Er 4.0 The correct statement is

a.
Impedance remain same to it's original value
I vaIue


c.
Impedance increase becomes twice of original value

d.
None of above




A non dispersive media has:

Group velocity> phase velocity
Group velocity phase velocity
Group velocity =phase velocity
None of above



A plane wave is characterized by:


c.345
(0.5 x +yeitrI2)eiwt-ikz e
The wave is
a.
Linearly Polarized

b.
Circularly Polarized

c.
Unpolarized

d.
Elliptically Polarized


If a right hand circularly polarised wave is incident on a perfect conductor. The reflected wave is: .
a.
Right circularly polarised wave

b.
Left circularly polarised wave

c.
Linear polarised wave
d None of above




.

--¥ffijSFcr INDiAN SPACE RESEARCH ORGANISATION Page 9 o{19



In which of the following cases the divergence of electric field is zero

a.
When electric field flows .uniform through open tubes




b. When electric field is released from the tube
o

c.
When electric field is within the closed tube o

d.
None of above



Skin depth at2.GHifofagOTa-cona-uctorwith a 4.55><107 S/m is 1.5 Jlm. Skin depth in Jlm at 8 GHz 18 GHz is:

a.
3.00, 4.50 b. 0.75,0.50 c. 0.375,0.055 d. 1.50, 1.00


The Smatrix of a lossless line having length is


a. 1 b. 1 c. j d. . None of Above
In the following Smith Chart,
Constant VSWR
circle


the movement from V along a constant VSWR circle to V1 needs addition of
a.
Capacitance in series with y

b.
CapacitanceTnsn"unfwithY

c.
TRL in series with y

d.
Stub with V



Page 10 of 19
INDIAN SPACE RESEARCH ORGANISATION·
----I-EbEQ"RGNICS-2012 SET-A

If the RF transmission is terminated in its impedance Zo which of the following statements is wrong:

a.
The input impedance of transmission line becomes Ze.

b.
The transmission line acts as an infinite long transmission line.

c.
The VSWR becomes one

d.
The VSWR becomes infinite.




The loss-less 1 quarter wavelength long 1 RF transmission of ch-aracteristic impedance 50 n is terminated in pure resistive load impedance 100 the input impedance is:

a.
5 n

b.
10 n

c.
250

d.
500n




A lossless matching circuit is shown in figure.



100 ohm
..

The values satisfying the matching condition are:
a.
XS1 -j25.1 Xp= +jl00 1 XS2 -j50

b.
XS1 +j25.1 Xp =-jl00 1 XS2

c.
XS1 -j25.1 Xp -jl00 1 XS2 -j50

d.
XS1 =+j25.1 Xp =+jl00 1 XS2 =+jl00


1
1
1
1

The true statement for wave propagation in rectangular wave guides filled with air is:

a.
The phase velocity is equal to velocity of light in air

b.
The phase velocity is always more than the velocity of light in air

c.
The phase velocity is always less than the velocity of light in air

d.
The phase velocity is un-defined.




As the wave frequency approaches to cut-off frequency of wave guide, the correct statement is

a.
The phase velocity of waves tends to zero.

b.
The phase velocity of waves tends to velocity of light.

c.
The phase velocity of waves tends to infinite.

d.
None of these.




The EM wave which does not propagate through a rectangular waveguide witha=30mm&-b=15mmis-: ...

a.
EM wave of frequency 4.5 GHz

b.
EM wave of frequency 5.5 GHz .

c.
EM wave of trequer}cy 50 GHz

d.
EM wave of frequency 300 GHz




The minimum input signal that gives output signal to noise ratio of 10 dB in a system that has an input impedance equal to 50 a noise figure of 4 dB and bandwidth of 100 KHz is 10.log(kTo) -174 dBm

a. 0.32 IlV b. 1.411lV c. 0.2451lV d. None of the above




.. INDIAN SPACE RESEARCH ORGANISATION Page 11 of 19.



LO I
Vout

Accos(wct)
In-phase
l

Power

13
Divider

LO
Am COs(Wmt) Iz
In this circuit, Vout is:
a. Upper Sideband (WL Wm
b.
c.
Both Upperand LowerSideband WL ± Wm)

d.
None of above


INDIAN SPACE RESEARCH ORGANISATION Page 12 of 19 .

I-UEtTRONICS -2012 SET-A

The RF amplifier A is having 3 dB NF 5 dB of gain, amplifier B is having 3.5 dB NF 15 dB . For overall noise figure of the cascaded system, the correct statement is

a.
A as first stage B as second stage offers minimum over all NF

b.
B as first stage A as second stage minimum over all NF

c.
Both the combination will offer same overall NF

d.
Over all NF will be less than 3 dB.




For this RF Circuit, the correct statement is


2.5

IF
GHz
140 MHz
RF
LO
2.64 GHz
a.
IF Spectrum is inverted and image fsat 2.780 GHz

b.
IF Spectrum is not inverted and image is at 2.780 GHz

c.
IF spectrum is inverted and image is at 2.360 GHz

d.
IF spectrum is not inverted and Image is 2.220 GHz


The gain of a parabolic dish antenna of 1 m diameter-and 80% efficiency at
9.5 GHz is:
a. 39 dB dB c. 40dB d. 45dB
e
In a uniform linear array, four isotropic radiating elements are spaced A/4 apart. The progressive phase shift between the elements required for forming the main beam at 600 of the end fire is

a.-n b. c. d.-n/8
The radiation resistance of a thin line centre fed A/2 antenna with sinusoid current distributionJs
a.
730

b.
73 +j42.50

c.
500

d.
750


INDIAN SPACE RESEARCH ORGANISATION
Page 13 of 19
To increase gain of a parabolic reflector antenna by 6dBi, the correct statement is Assuming efficiency
a.
Diameter is to be increased to 6 folds

b.
Diameter is to be increased to 4 folds

c.
Diameter is to be increased to 2 folds

d.
None of above


...
a.
An Isolator

b.
T/R switch in trans-receiver

c.
Adjustable Phase Shifter

d.
All of these


The microwave device working on the principal of Faraday rotation is called as:
a.
Rotary joint

b.
Circulator

c.
Isolator

d.
None of these


Q.

The phase difference between adjacent anode poles of Magnetron is generally:

a.
Zero radians

b.
n/4 radians

c.
n/2 radians

d.
n radians




Which of the following devices cannot be used as microwave oscillator:

a.
IMPATT diode

b.
PN Junction .diode
c.TRPATT diode·


d.
BARRITT diode




For a Phase locked loop system, the open loop transfer function is



SET-A
1000


The phase margin is 50° and crossover frequency is approximately 1000 rad/s. A time delay is introduced in the phase detector reducing the phase margin to 40°. The maximum permissible time delay in seconds) is
..
a.
10-4

b.
0.174

c.
1.192xl0-3

d.
0.174xl0-3



In this circuit, the relationship between Vi &Va is:

a.

b.

c.


d. None of these


Output Impedance of a source follower is:

a.
119m rd

b.
rc1(l 9m.rd)


c.
rd

d.
None






-INDIANSPACE'RESEARCH ORGANISATION
PagelS of 19
. ..
"
.. ..."
For a negative feedback system shown in Figure, s

the equivalent transfer function is S3 SS2 6s

a. b.
s3+7s2 +12s+3 S3 SS2 S2 Ss 4 S2 +Ss
c.

d.


If (146)x (246)8 then the value of base x is:

a.5 b.6 c. 7 d.9


The truth table for implementing a boolean variable ris given by


1
C B A F
a a a d
a a 1 1
a 1 a 1·
a 1 1 d
1 a a a
1 a 1 a
1 1 a a
1 1 1 1

where d represents don't care states. The minimized expression for F is
a.
E.C ....

b.
A.B+C

c.
A.B.C +A.B.C +A.B.C


d. None of above


.._...
Page16 of19 .. .
INDIAN SPACE RESEARCH ORGANISATION·
-··1· ELECTRONICS -2012 SET,-A
The state transition diagram for a sequence generator is shown in figure

It is designed using D F/Fs and combinational logic blocks L1, L2 &L3 and is initialized at Q1 Qo

The minimized expressic:lns for 00, 01 02 are:
a. O2=Q2 01=QI 00=Qo


d. None of above

The number of comparators needed in a 8-bit flash type A to D converter is

a. 8 b.16 c.255 d. 256


The register in the 8085A that is used to keep track of the memory address of the next op-code to be run in the program is the:

a.

b.

c.

d.




stack pointer
program counter accumulator
None of above
..... ...
.... ...

Page 17 of 19
INDIAN SPACE RESEARCH ORGANISATION


The Complement Accumulator instruction of 8085 processor on execution affects

a. Zero Flag b. Sign Flag c. Carry Flag d. None of the flags


"Cycle Stealing' in microprocessor parlance refers to

a.
Special type of DMA access by an external device

b.
RESET operation at power ON by microprocessor

c.
Interrupt Acknowledge cycle
d.noneof-ahover­




Principle of "locality" is used in context of

a.
Addressing lowest Memory address by microprocessor

b.
Addressing Highest Memory.address by microprocessor

c.
Accessing Cache memory locations.

d.
None of above.




IfA, B Care vectors and A =l.ux 2.uy 3.uz, B =1.ux 1.uy l.uz and 3.ux 2.uy 1.uz, then x B).C is: .

a. 2 b. 1 c.0 d.


The system of equations x 2 x y+z x 8 has

a.
A unique solution

b.
No solution






c.
An infinite number of solutions

d.
None of these


+ey+ey +··..··

y
If
dy
then is
dx
a. b. c. l/x d.
The area boundedbythecurvesJC=X, Y=x is given by_
a. 2/3 b. 1/2 c. 1/6 d. 1/3

INDIAN SPACE RESEARCH ORGANISATION Page 18 of 19

2012
SET-A
. The eigen values of the matrix are
sina][sma cosa
a. ±cosa b. ± sin a c. tan a cot a d. cosa ± sin a
The Laplace Transform of formed by convolution operator is:
{cos2m.u(t)}
a. 4 b. 2 11j[ S S2 41(2
c. (52
2

A random variable X has X CYX . Form a new random variable Y=2 X 1. The values of y CY/ are:

a. 0&1 b. 1 &2 c. 1&4 d. None of these


Person X can solve 80% of thelSRO question paper and Person Y can solve 60%. The probability that at least one of them will solve a problem from the question paper, selected,at random is


a.0.48 b. 0.70 c. 0.88 d. 0.92
e

INDIAN SPACE RESEARCH ORGANISATION
Page 19 of 19
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