ISRO Scientist or Engineer Electronics Dec 2017

ISRO Scientist or Engineer Electronics Dec 2017 - Question 1

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Find the area of the region bounded by the curves $$y = x^{2}, y = \frac{1}{x}$$ and $$x = \frac{1}{2}$$ (see in graphical representive figure)

A

$$\frac{\ln 2-7}{24}$$

B

$$\frac{\ln 2+7}{24}$$

C

$$\frac{\ln 3-5}{24}$$

D

$$\frac{\ln 3+5}{24}$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 2

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Find the Eigen values $$\lambda$$ in the system $$\begin{bmatrix}4 & 1 \\3 & 2 \end{bmatrix}$$ $$\begin{bmatrix} x \\ y \end{bmatrix}$$ =\lambda $$\begin{bmatrix} x \\ y \end{bmatrix}$$

A

1 and 5

B

4 and 3

C

1 and 2

D

2 and 4

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 3

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Find the transient response of a pair of complex poles as given below

A

B

C

D

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 4

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A random variable z , has a probability density function f(z) where $$f(Z) =e^{-z} O\leq Z < \infty$$ the probability of $$O \leq Z \leq 2$$ will be approximately

A

0.368

B

0.135

C

0.393

D

0.865

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 5

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Evaluate $$\lim_{x \rightarrow 2} \frac{\sqrt{x^{2}+5-3}}{x^{2}-2x}$$

A

$$\frac{1}{3}$$

B

$$\infty$$

C

-3

D

0

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 6

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What is the R.M.S of following waveform if the average value is zero?

A

$$\sqrt{\frac{17}{13}}$$

B

$$\sqrt{\frac{8}{3}}$$

C

$$\sqrt{\frac{5}{3}}$$

D

$$\sqrt{\frac{1}{3}}$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 7

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A radar system uses TWTA as high power RF source for transmitting 300W Peak Power. The efficiency of transmitter during pulse is 75% and the transmit duty is 25%. If the DC
power required during pulse off period is 20W. The average power dissipation in TWTA is

A

81.25 W

B

125 W

C

50 W

D

40 W

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 8

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The ramp signal $$(V_{t} : 0 to 5V)$$ is compared with the Soft-Start Signal provided by N-channel MOSFET $$(Q_{1} )$$ for Amplifier $$( A_{1} )$$ output. If $$Q_{1}$$ having low threshold voltage of 0.7V and 1 negligible ON resistance. What is the duty of $$c_{1}$$ output signal of comparator $$(C _{1})$$ after $$100 \mu$$ Sec?

A

17.4 %

B

34.8 %

C

0 %

D

50 %

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 9

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A High speed digital Subsystem requires three voltages $$V_{1} , V_{2}$$ and $$V_{3}$$ with 1 : 2 : 1 power 3 ratings respectively. The power supply is designed with the distribute power conversion scheme as shown in the following figure. What is the overall power conversion efficiency?

A

$$\frac{4 \times \eta_{1} \times \eta_{2} \times \eta_{3}}{\eta_{2} \eta_{3}+2 \times \eta_{3}+\eta_{2}}$$

B

$$\frac{\eta_{1} \times \eta_{2} \times \eta_{3}}{\eta_{2} \eta_{3}+2 \times \eta_{3}+\eta_{2}}$$

C

$$\frac{4 \times \eta_{1} \times \eta_{2} \times \eta_{3}}{\eta_{2} \eta_{3}+ \times \eta_{2}+\eta_{3}}$$

D

$$\frac{2 \times \eta_{1} \times \eta_{2} \times \eta_{3}}{\eta_{2} \eta_{3}+ \times \eta_{2}+\eta_{3}}$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 10

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If the transformer and diodes in the following circuit are ideal, Find out the value of Capacitor (Co) provides 5% ripple voltage across $$R_{L}$$.
(Assume that $$\sin^{-1} (0.95) \sim \frac{2 \pi}{5}$$ in Radians $$\ln(0.95) = -0.051$$)

A

$$4.7 \mu F$$

B

$$16.7 \mu F$$

C

$$8.7 \mu F$$

D

$$2.7 \mu F$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 11

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Relationship between doppler frequency shifts of two radars A and B having 0.1 foot and 0.05 foot wavelengths, approaching the target at 1000 feet per second and 2000 feet per
second rate respectively, will be

A

Doppler frequency shift of radar A will be one-fourth of doppler frequency shift of radar B

B

Doppler frequency shift of radar A will be one-half of doppler frequency shift of radar B

C

Doppler frequency shift of radar A will be double of doppler frequency shift of radar B

D

Doppler frequency shifts of radar A and radar B will be same

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 12

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A sinusoidal input which can be reproduced in an OP-AMP without any distortion having slew rate of $$10 \pi \frac{V}{\mu s}$$ and 5V peak output amplitude, has the maximum frequency of

A

1KHz

B

1MHz.

C

31.42KHz.

D

31.42MHz.

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 13

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Which of the following is NOT a characteristic of Schottky Diode?

A

Thermionic emission of carriers across Schottky barrier

B

Current conduction in Schottky diodes is by majority carriers

C

Switching speed of Schottky diodes is less compared to p-n junction diodes

D

Schottky diode comprises of Metal-Semiconductor junction

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 14

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A Sensistor exhibits the following characteristics

A

Either increase or decrease in resistance value with increase in temperature based on the material type used in the thermistor

B

Always increase in resistance value with increase in temperature

C

Always decrease in resistance value with increase in temperature

D

No change in resistance value with temperature

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 15

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When an electromagnetic wave is incident on an object having surface roughness comparable to the wavelength, then

A

Specular reflection occurs

B

Absorption occurs

C

Diffused scattering occurs

D

None of the above

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 16

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For the following circuit, determine the output voltage $$‘V_{0}’$$ in terms of input voltages $$V_{1}$$ and $$V_{2}$$ , assuming $$A_{1} and A_{2}$$ are ideal op-amps

A

$$11 V_{2}-V_{1}$$

B

$$ V_{2}-11V_{1}$$

C

$$(V_{2}-V_{1})$$

D

None of the above

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 17

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Dominant mechanism for motion of charge carriers in forward and reverse biased silicon p-n junctions are

A

Drift in forward bias, diffusion in reverse bias

B

Diffusion in forward bias, drift in reverse bias

C

Diffusion in both forward and reverse bias

D

Drift in both forward and reverse bias

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 18

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Which of the following is NOT true about opto-couplers?

A

It is a solid state device to isolate two parts of a circuit

B

It can act as an input device or output device but not both

C

Combines a Light Emitting Diode and a Photo Transistor in a single package

D

It prevents electrical noise or voltage transients of one circuit from integrating with other circuit

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 19

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Which of the noise types is dominant in Metal Semiconductor Field Effect Transistor (MESFET) when compared to Bipolar Junction Transistor (BJT)?

A

Thermal Noise

B

Shot Noise

C

Flicker Noise

D

All of the above

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 20

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Which factor determines the range resolution of a radar?

A

Size of the antenna

B

Bandwidth of the transmitted pulse

C

Power radiated form the antenna

D

Centre frequency of the radar

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 21

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A signal having frequency component from DC-2KHz is to be Pulse code Modulated with a 6 bit Encoder. Minimum carrier bandwidth required is?

A

4KHz.

B

128KHz.

C

16KHz.

D

12KHz.

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 22

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Which of the following is NOT true for Schmitt Trigger?

A

Schmitt trigger can be used as Sine-to-Square Wave Converter

B

Schmitt trigger uses OP-AMP in Open Loop Mode

C

Hysteresis exists in Schmitt Trigger

D

All of the above

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 23

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For the silicon transistor shown in the figure below, the value of $$I_{B}$$ is?

A

26.47 $$\mu A$$

B

52.94 $$\mu A$$

C

13.235 $$\mu A$$

D

30.11 $$\mu A$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 24

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Which one of the following statement is not true for static random access memory (SRAM)

A

Static RAM stores data in the form of charge

B

They have low capacity, but offer high speed

C

It doesn’t require periodic refreshing

D

They are made up of six CMOS transistor

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 25

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Which of the following statement is not true

A

Autocorrelation function and energy spectral density forms a Fourier transform pair

B

Autocorrelation function of a real valued energy signal is a real valued odd function

C

The value of autocorrelation function of a power signal at the origin is equal to the average power of the signal

D

Autocorrelation function is the inverse Fourier transform of power spectral density

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 26

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The Eddy current loss is proportional to the

A

Frequency

B

Square of the frequency

C

Cube of the frequency

D

Square root of the frequency

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 27

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The temperature below which certain materials are antiferromagnetic and above which they are paramagnetic is called

A

Weiss temperature

B

Curie temperature

C

Neel temperature

D

None of the above

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 28

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In metals, the thermal conductivity K and electrical conductivity $$\sigma$$ are related as $$ \frac{K}{\sigma T} = L$$  is Known as the flux density is increased from 0 to 2.5 T,$$\mu_{r}$$ will

A

Lattice constant

B

Lorenz number

C

Lanevin Function

D

Larmor number

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 29

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In a specimen of ferromagnetic material with saturation magnetization as 8000 Gauss, as the flux density is increased from 0 to 2.5 T, $$\mu_{r}$$ will

A

Increase

B

Decrease

C

First decrease then increase

D

First increase then decrease

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 30

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The cavity magnetron uses strapping to

A

Prevent mode jumping

B

Prevent cathode back-heating

C

Ensure bunching

D

Improve the phase focussing effect

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 31

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The TWT is sometimes preferred to the magnetron as a radar transmitter output tube because it is

A

Capable of a larger duty cycle

B

A more efficient amplifier

C

More broadband

D

Less noisy

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 32

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One of the reason why conventional vacuum valve tubes not used at microwave frequencies is that their

A

Noise increases

B

It has less transit time

C

Shunt capacitive reactance become too large

D

Series induction reactance become too small

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 33

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In a telecommunication trans-receive system, the transmitting antenna with antenna aperture of 1m is fed with 1W of power at 10GHz. The receive antenna with antenna aperture of 0.5m located at 1km away receives x mW of power. If the transmitting frequency changes to 20GHz, what will happen to receive power?

A

Increase by 3dB

B

Increase by 6dB

C

Decrease by 3dB

D

Decrease by 6dB

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 34

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Find the maximum directivity of an antenna whose power density is given by $$W_{rad}= \hat{a} \frac{A_{o} \sin \theta}{r^{2}}$$ $$\frac{W}{m^{2}}$$ where $$A_{o}$$ is peak value of power density $$\theta$$ is the usual spherical coordinate and $$hat{ar}$$ is the radial unit vector

A

$$\frac{4}{\pi}$$

B

$$\frac{2}{\pi}$$

C

$$\frac{3}{\pi}$$

D

$$\frac{5}{\pi}$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 35

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A DC series motor is driven by a chopper circuit. The supply voltage is 220 V and the duty cycle is 25%. Determine the DC voltage applied to the motor

A

165 V

B

55 V

C

220 V

D

110 V

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 36

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A single-phase full-wave AC phase controller feeds power to a resistive load of 100 Ω from a 220 V, 50 Hz supply. What will be the R.M.S. output voltage at delay angles $$\alpha_{1}=\alpha_{2}=\alpha=\frac{\pi}{2}$$ of both transistors?

A

$$\frac{220}{\sqrt{2}}$$ V

B

$$\sqrt{2 \times 220}$$ V

C

$$\sqrt{2} \times 110 V $$

D

$$\sqrt{2} \times 220 V $$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 37

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A half-wave rectifier is used to charge a 12 V battery through a resistance ‘R’. The input transformer is fed by 34 V AC with turns ratio 2:1. Calculate the conduction period of the diode.

A

$$136^\circ$$

B

$$120^\circ$$

C

$$173^\circ$$

D

$$137^\circ$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 38

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Two signals $$f_{a}$$ and $$f_{b}$$ are given as input to EX-OR to measure phase difference. The average output voltage will be

A

B

C

D

None of the above

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 39

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In the following circuit, find the output voltage $$V_{o}$$

A

$$\frac{R_{A}}{R_{B}} \times I_{in} \times R_{s}$$

B

$$I_{in}\times R_{s} \times (1+\frac{R_{A}}{R_{B}})$$

C

$$\frac{R_{B}}{R_{A}} \times I_{in} \times R_{s}$$

D

$$I_{in}\times R_{s} \times (1+\frac{R_{B}}{R_{A}})$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 40

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From the following Relative amplitude vs Frequency plot, identify the type of noise which the sections A, B, C & D depict

(i) Thermal Noise (ii) Power line pick up
(iii) Power supply (EPC) switching noise (iv)1/f noise

A

A-i, B-ii, C-iii, D-iv

B

A-ii, B-i, C-iv, D-iii

C

A-iv, B-ii, C-iii, D-i

D

A-iii, B-iv, C-ii, D-i

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 41

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Y-parameter of a two port network is shown below. A 1 Ω resistor is connected to the network as shown. Find out the Y parameter of the whole network.

A

$$\begin{bmatrix}6 & 1 \\0 & 4 \end{bmatrix}$$

B

$$\begin{bmatrix}6 & 3 \\2 & 4 \end{bmatrix}$$

C

$$\begin{bmatrix}4 & 1 \\0 & 2 \end{bmatrix}$$

D

$$\begin{bmatrix}3 & 1 \\1 & 2 \end{bmatrix}$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 42

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For the circuit shown below, $$Z_{1}=K_{1} \times \frac{(s+2)}{(s+5)}$$. Find $$ Z_{2}$$, where $$K_{1}$$ and $$K_{2}$$ are constants containing circuit element values

A

$$K_{2} \times \frac{s}{s+5}$$

B

$$\frac{(s+5)}{(s \times K_{2})}$$

C

$$K_{2} \times \frac{s}{s+6}$$

D

$$\frac{(s+6)}{s \times K_{2}}$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 43

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Following is the small signal high frequency equivalent circuit of a common source amplifier $$\frac{V_{o}}{V_{i}}$$ will be of the form
$$(K, Z_{1},a_{o},a_{1},a_{2},a_{3}$$, are constants containing circuit elements)

A

$$\frac{K(s-Z_{1})}{a_{o}+a_{1}s+a_{2} s^{2}}$$

B

$$\frac{K.s}{(a_{o}+a_{1}s+a_{2} s^{2}+a_{3} s^{2})}$$

C

$$\frac{K(s-Z_{1})}{a_{o}+a_{1}s}$$

D

$$\frac{K}{a_{o}+a_{1}s}$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 44

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Phase of the transfer function of the following circuit is

A

$$\tan^{-1} (\frac{1}{\omega RC})$$

B

$$\tan^{-1} (\omega R C)$$

C

$$\tan^{-1} (\frac{RC}{\omega})$$

D

$$\tan^{-1} (\frac{\omega}{RC})$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 45

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The error in measurement of a dc voltmeter with input signal: 1.5 V, voltage range: 2 V, accuracy : $$\pm$$ (25 ppm of reading + 5 ppm of range) is

A

$$\pm 50 \mu V$$

B

$$\pm 30 \mu V$$

C

$$\pm 47.5 \mu V$$

D

$$\pm 10 \mu V$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 46

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Consider the signal $$x(t)= \begin{cases}2\cos (t)+ \cos(2t) & t < 0\\2\sin (t)+ \sin(2t) & t \geq 0\end{cases}$$

The signal X(t) is:

A

periodic with period = $$2\pi$$

B

periodic with period =$$\pi$$

C

non-periodic

D

periodic with period = $$\frac{\pi}{2}$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 47

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The system y(t)=x(2t)+3 is

A

Linear and Time Invariant

B

Causal and Linear

C

Non-Linear and Time Variant

D

Linear and memoryless

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 48

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Consider the system $$R[m]=\sum_{n=0}^{N-1} Y[n] x[n-m]$$ where y[n] and x[n] are real periodic signals with period N. The above output can be obtained using

A

$$ IFFT\left\{FFT[Y] \times conj(FFT[X])\right\}$$

B

$$IFFT\left\{FFT[Y] \times FFT[X]\right\}$$

C

$$IFFT\left\{FFT[Y] \times (FFT[-X])\right\}$$

D

$$IFFT\left\{FFT[-Y] \times (FFT[X])\right\}$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 49

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Consider the system defined by $$\frac{d^{2}y}{dt^{2}}+(a+b)\frac{dy}{dt}+ab=x(t); a>0,b>0$$ can be realized using which impulse response function

A

$$h(t)=(e^{-at}+e^{-bt})u(t)$$

B

$$h(t)=(e^{-at} \times e^{-bt})u(t)$$

C

$$h(t)=(e^{at}+e^{-bt})u(t)$$

D

$$h(t)=e^{-(a+b)t} u(t)$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 50

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A continuous time signal has frequency content at f = 10MHz, 50MHz and 70MHz. The signal is sampled at sampling frequency of 56MHz. The frequency content of output will be

A

10MHz

B

10MHz and 6MHz

C

10MHz, 6MHz and 14MHz

D

46MHz

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 51

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Consider the system with x(t) as input and y(t) as output. The frequency domain characteristics are shown in the figure. Which combination of A and B will give y as result?

A

B

C

D

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 52

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The $$R = \frac{1}{3}$$ convolution encoder defined by transfer functions
$$H_{1}(Z) =1+Z^{-1}$$
$$H_{2}(Z) =1+Z^{-2}$$
$$H_{3}(Z) =1+Z^{-1}+Z^{-2}$$

A

recursive and K = 3

B

systematic and K = 2

C

non-recursive and K = 3

D

non-recursive and K = 2

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 53

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The match filter response for given signal sampled at t = T is

A

B

C

D

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 54

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Characteristic equation of H(s) is given as $$3s^{4}+2s^{3}+5s^{2}+s+2=0$$ is

A

unstable

B

stable

C

all poles in right half plane

D

unstable with only one pole in right half plane

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 55

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Consider the feedback system 

$$G(s) = \frac{K(s + 4)}{s(s + 1)}  H(s) = \frac{1}{s + 2}$$

The value of gain for which system is marginally stable is

A

K = 4

B

K = 6

C

K = 10

D

K = 2

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 56

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Consider the Bode plots (magnitude and phase) of two different open loop transfer functions of two unity feedback systems. The open loop transfer functions have poles in right half plane. The closed loop system formed from these open loop systems. Which of the following holds true?

A

Closed loop system with I is stable and with II is unstable

B

Closed loop systems using I and II both are unstable

C

Closed loop system with I is unstable and II is stable

D

Closed loop system with I and II are stable

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 57

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The steady state response for an input X(s) = K/s to a system whose transfer function is H(s) in time domain is
$$H(s)=\frac{1}{(s+5)(s+2)}$$

A

$$\frac{K}{10}$$

B

$$e^{-5t} u(t)$$

C

$$e^{-2t} u(t)$$

D

$$(e^{-5t}+e^{-2t}) u(t)$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 58

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Consider a closed loop stable phase locked loop system as shown in the diagram below

The system is capable of producing zero steady state error E(t) for

A

Phase step only

B

Constant velocity and phase step

C

Acceleration

D

Jerk

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 59

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The modes in a reflex klystron

A

Result from excessive oscillating frequencies of the cavity

B

Correspond to different oscillating frequencies of the cavity

C

Are caused by spurious frequency modulation

D

All give much the same frequency but different transit times

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 60

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A dielectric is subjected to alternating electric field. The dielectric losses are proportional to

A

Real part of the dielectric constant

B

Imaginary part of the dielectric constant

C

Both Real and Imaginary part of the dielectric constant

D

None of the above

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 61

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The electric field of a linearly polarized electromagnetic wave is given by $$E_{i}=\hat{a_{x}}E_{o}(x,y)e^{-jkz}$$ is incident upon a linearly polarized antenna whose electric field polarization is expressed as $$E_{a}=(\hat{a_{x}}+\hat{a_{y}}) E(r,\theta,\phi)$$.Find the polarization loss factor.

A

$$\frac{1}{2}$$

B

$$\frac{3}{2}$$

C

$$\frac{2}{3}$$

D

$$\frac{1}{4}$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 62

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A lossless T-junction two way power divider has a source impedance, input transmission line impendence and $$\frac{o}{p}$$ port load impendence of 50 Ω. Find the output characterization impedances so that the input power is divided in a 2:1 ratio.

A

$$ Z_{1}=150 Ω Z_{2}=75 Ω$$

B

$$ Z_{1}=50 Ω Z_{2}=100 Ω$$

C

$$ Z_{1}=60 Ω Z_{2}=120 Ω$$

D

$$ Z_{1}=30 Ω Z_{2}=60 Ω$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 63

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Following circuit implements a

A

De-Multiplexer

B

Multiplexer

C

$$ Y=I_{0}(A_{o}+A_{1})$$

D

$$ Y=I_{0}(\overline {A_{1}}+A_{0})$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 64

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The frequency of the output Y is

F : clock freq.

M : input

X : 32 bit register

A

$$\frac{MF}{2^{32}}$$

B

$$\frac{2MF}{2^{32}}$$

C

$$\frac{F}{2^{32}}$$

D

$$\frac{2^{32}F}{M}$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 65

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Consider the output A and B with $$I_{0},I_{1},I_{2}$$ and $$I_{3}$$ as input
$$A=\overline{I_{3}} \overline{I_{2}} I_{1}+I_{3}$$
$$B=\overline{I_{3}} I_{1}+I_{3}$$
The above circuit is

A

4:1 Multiplexer

B

De-Multiplexer

C

BCD circuit

D

Priority Encoder

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 66

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The output Z =

A

$$A \overline{\overline{c}} AB$$

B

ABC

C

$$ABC+A \overline{\overline{c}} B$$

D

$$ABC+\overline{\overline{c}}B$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 67

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Consider the shift register

The frequency of signal x is fs and the shift register is clocked at the positive edge of 2fs. The time offset between A and B is

A

$$\frac{1}{(2fs)}$$

B

$$\frac{1}{(fs)}$$

C

$$\frac{3}{(2fs)}$$

D

$$\frac{1}{(4fs)}$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 68

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The circuit is formed as shown below. The output S and C implement

A

Two bit adder with sum and carry respectively

B

Two bit subtractor with sum and borrow respectively

C

$$S=AB+\overline{A} \overline{B};C=\overline{A} B$$

D

None of the above

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 69

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What is the value of the register formed from D flip-flops using $$Q_{0},Q_{1}$$, and $$Q_{2}$$ as output $$(Q_{0},Q_{1},Q_{2})$$ after 14 cycles

A

110

B

000

C

001

D

011

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 70

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The 4:1 Multiplexer implemented as

A

$$\sum {(1,6,3,7)}$$

B

$$\sum {(1,2,5,7)}$$

C

$$\sum {(2,3,4,5)}$$

D

$$\sum {(1,3,4,7)}$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 71

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In a digital circuit the set-up time violation can be fixed by

A

Increasing the clock frequency

B

Increasing the delay of data path logic

C

Slowing the clock frequency

D

None of the above

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 72

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Number of J-K flip flops in modulo 16 binary up-counter are

A

16

B

4

C

8

D

2

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 73

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The solid angle subtended by the sun as viewed from the earth is Ω =$$4 \times 10^{-5}$$ steradian.
A microwave antenna designed to be used for studying the microwave radiation from the
sun has a very narrow beam whose equivalent solid angle is approximately equal to that
subtended by the sun. What is the approximate directivity, D?

A

$$10^{5}$$

B

$$\pi \times 10^{5}$$

C

$$\pi \times 10^{6}$$

D

$$10^{6}$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 74

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A gain-standard horn is known to have a gain G = 10. It is being used to measure the gain of a large directional antenna by the comparison method. When the antenna being measured is connected to the receiver it is found to be necessary to insert an attenuator adjusted to attenuate by 23 dB in order to have the same receiver output that was observed with the horn connected. What is the gain of the large antenna?

A

13 dB

B

23 dB

C

33 dB

D

230 dB

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 75

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A paraboloidal-reflector antenna is designed for operation at 3 GHz. Its largest aperture dimension is 20 feet. It is desired to build a scale model of this antenna with the largest aperture dimension scaled to 18 inches. At what frequency must this model be operated in order to have the same pattern as the full-size antenna?

A

10 GHz

B

20 GHz

C

40 GHz

D

4 GHz

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 76

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An antenna has a radiation resistance of 72 Ω ,a loss resistance of 8 Ω and power gain of 16.Calculate its directivity.

A

15.8

B

16.8

C

17.8

D

18.7

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 77

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The current density at the surface of a thick metal plate is 100 $$\frac{A}{m^{2}}$$ What is the skin depth if the current density at a depth of 0.0059 cm is 0.272 $$\frac{A}{m^{2}}$$?

A

8 $$\mu m$$

B

10 $$\mu m$$

C

15 $$\mu m$$

D

20 $$\mu m$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 78

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An air filled rectangular waveguide $$R_{1}$$ is operating at the frequency 2 GHz and another air filled rectangular waveguide $$R_{2}$$ is operating at 4 GHz. The guide wavelengths of these waveguides at their respective frequencies are equal. If the cut-off frequency of waveguide $$R_{1}$$ is 1 GHz, what is the cut-off frequency of the waveguide $$R_{2}$$ in GHz?

A

$$\sqrt{10}$$

B

$$\sqrt{11}$$

C

$$\sqrt{12}$$

D

$$\sqrt{13}$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 79

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An electromagnetic wave propagates through a lossless insulator with a velocity $$1.5 \times 10^{10} \frac{cm}{s}$$ . Calculate the electric and magnetic properties of the insulator if its intrinsic impedance is 90 $$\pi$$ ohms

A

$$\epsilon_{r}=2.26 and \mu_{r}=1.5$$

B

$$\epsilon_{r}=1.5 and \mu_{r}=2.26$$

C

$$\epsilon_{r}=1.2 and \mu_{r}=2.0$$

D

$$\epsilon_{r}=2.0 and \mu_{r}=1.2$$

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ISRO Scientist or Engineer Electronics Dec 2017 - Question 80

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A square waveguide carries $$TE_{11}$$ mode whose axial magnetic field is given by $$H_{Z}=H_{o} \times \cos (\frac{\pi x}{\sqrt{8}}) \times \cos (\frac{\pi y}{\sqrt{8}})$$ A/m where waveguide dimensions are in cm. What is the cut-off frequency of the mode?

A

5.5 GHz

B

6.5 GHz

C

7.5 GHz

D

8.5 GHz

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