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Microwave Communication MCQ Questions & Answers

Microwave Communication MCQs : This section focuses on the "Microwave Communication". These Multiple Choice Questions (MCQs) should be practiced to improve the Microwave Communication skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.




Question 1

Assertion (A): The phenomenon of differential mobility is called transferred electron effect.Reason (R): GaAs exhibits transferred electron effect.

A. Both A and R are correct and R is correct explanation of A
B. Both A and R are correct but R is not correct explanation of A
C. A is correct but R is wrong
D. A is wrong but R is correct

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Question 2

The fabrication of microstrip line is done by

A. photo etching
B. printed circuit technique
C. oxidation
D. cladding

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Question 3

As the frequency is increased, the charging MVAR in a cable

A. decreases
B. increases
C. remain the same
D. decreases or remains the scheme

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Question 4

In a klystron amplifier dc electron velocity is v0 and dc electron charge density is r0 the dc beam current is

A. r0v0
B. r0/v0
C. v0/r0
D. (v0/r0)2

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Question 5

In a backward wave oscillator the wave travelling along the line winds itself back and forth

A. TRUE
B. FALSE

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Question 6

The action of backward wave oscillator is similar to that of

A. klystron amplifier
B. reflex klystron oscillator
C. TWT
D. magnetron

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Question 7

A waveguide section in a microwave circuit acts as

A. LP filter
B. Bandpass filter
C. HP filter
D. Band stop filter

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Question 8

Which of the following is not a travelling wave?

A. e = Em sin (βx - ωt)
B. e = Em cos (βx - ωt)
C. e = Em sin (ωt - βx)
D. e = Em sin (βx)

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Question 9

Reflex klystron oscillator is essentially a low power device

A. TRUE
B. FALSE

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Question 10

A line has a phase constant of 29.8 rad/m. At 1000 MHz the wavelength is

A. 29.8 m
B. 2.98 m
C. 2.1 m
D. 0.21 m

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Question 11

Assertion (A): A coaxial line is a non-radiating line.Reason (R): In a coaxial line the electric and magnetic fields are confined to the region between the concentric conductors.

A. Both A and R are correct and R is correct explanation of A
B. Both A and R are correct but R is not correct explanation of A
C. A is correct but R is wrong
D. A is wrong but R is correct

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Question 12

A resistive microwave load with ZL = 150 Ω is connected to 50 Ω coaxial line. SWR is

A. more than 3
B. less than 3
C. equal to 3
D. either (a) or (c)

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Question 13

Assertion (A): The reverse saturation current in a semiconductor diode is 4nA at 20°C and 32 nA at 50°C.Reason (R): The reverse saturation current in a semiconductor diode doubles for every 10°C rise in temperature.

A. Both A and R are correct and R is correct explanation of A
B. Both A and R are correct but R is not correct explanation of A
C. A is correct but R is wrong
D. A is wrong but R is correct

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Question 14

In a klystron amplifier the input cavity is called

A. buncher
B. catcher
C. Pierce gun
D. collector

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Question 15

In a travelling wave tube distributed interaction between an electron beam and a travelling wave takes place

A. TRUE
B. FALSE

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Question 16

In a directional coupler

A. isolation (dB) equals coupling plus directivity
B. coupling (dB) equals isolation plus directivity
C. directivity (dB) equals isolation plus coupling
D. isolation (dB) equals (coupling) (directivity)

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Question 17

In a TWT the amplitude of resultant wave travelling down the helix

A. increases exponentially
B. increases linearly
C. decreases exponentially
D. is almost constant

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Question 18

Which TM mode in rectangular waveguide has lowest cutoff frequency?

A. TM11
B. TM01
C. TM10
D. TM21

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Question 19

A quarter wave line open circuited at far end behaves as

A. inductance
B. L and C in parallel
C. capacitance
D. L and C in series

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Question 20

Which of the following parameters is negligible in transmission lines?

A. R
B. L
C. C
D. G

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Question 21

Which of the following devices uses a slow wave structure?

A. Klystron two cavity amplifier
B. Klystron multicavity amplifier
C. Reflex klystron oscillator
D. TWT

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Question 22

A loss less line of characteristic impedance Z0 is terminated in pure reactance of -jZ0 value. VSWR is

A. 10
B. 2
C. 1
D. infinity

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Question 23

Microwave resonators are used in

A. microwave oscillators
B. microwave narrow band amplifier
C. microwave frequency metres
D. all of the above

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Question 24

The diagram to show distance time history of electrons in klystron amplifier is called

A. apple gate diagram
B. asynchronous diagram
C. bunching diagram
D. velocity modulation diagram

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Question 25

In a turnstile antenna two-half wave resonant wire radiators are placed at 90° to each other in the same plane and are excited

A. in phase
B. in phase opposition
C. 90° out of phase with each other
D. 45° out of phase with each other

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Question 26

A line has Z0 = 300 ∠ 0° Ω. If ZL = 150 ∠ 0° Ω, reflection coefficient is

A. 0.5
B. 0.3333
C. -0.3333
D. -0.5

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Question 27

In a microstrip transmission the signal can be easily redirected by changing the centre strip.

A. TRUE
B. FALSE

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Question 28

Which of the following lines is non-radiating?

A. Open two wire
B. Coaxial
C. Both
D. None of the above

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Question 29

The velocity factor of a transmission line depends on

A. temperature
B. skin effect
C. relative permittivity of dielectric
D. none of the above

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Question 30

A 10 km long line has a characteristic impedance of 400 ohms. If line length is 100 km, the characteristic impedance is

A. 4000 Ω
B. 400 Ω
C. 40 Ω
D. 4 Ω

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Question 31

Assertion (A): The reverse saturation current in a semiconductor diode is 4nA at 20°C and 32 nA at 50°C.

A. Both A and R are correct and R is correct explanation of A
B. Both A and R are correct but R is not correct explanation of A
C. A is correct but R is wrong
D. A is wrong but R is correct

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Question 32

The width of a radio beam from a 1 m diameter parabolic antenna at 10 GHz is about

A. 100°
B. 50°
C. 5°
D. 1°

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Question 33

Which of the following devices uses a helix?

A. Klystron amplifier
B. Klystron oscillator
C. TWT
D. Both (a) and (b)

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Question 34

Assertion (A): Artificial transmission lines are frequently used in laboratories.Reason (R): An artificial transmission line can be used to represent an actual line and can also be used as a delay circuit, as attenuator, as filter network etc.

A. Both A and R are correct and R is correct explanation of A
B. Both A and R are correct but R is not correct explanation of A
C. A is correct but R is wrong
D. A is wrong but R is correct

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Question 35

Skin effect is more pronounced at high frequencies.

A. TRUE
B. FALSE

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Question 36

The frequency of oscillation in a backward wave oscillator can be changed by

A. varying the voltage which controls beam velocity
B. varying the beam current
C. both by varying the beam current and by light varying the voltage which controls beam velocity
D. changing the rate of thermionic emission

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Question 37

The reflection coefficient on a line is 0.2 ∠45°. The SWR is

A. 0.8
B. 1.1
C. 1.2
D. 1.5

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Question 38

Both Impatt and Trapatt devices use avalanche effect

A. TRUE
B. FALSE

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Question 39

A line is excited by a 100 V dc source. If reflection coefficients at both ends are 1 each then

A. there will be no oscillations on line
B. there will be only 1 or 2 oscillations on line
C. there will be a finite number of oscillations on line
D. the oscillations will continue indefinitely

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Question 40

In a three cavity klystron amplifier, the oscillations are excited in

A. input cavity
B. output cavity
C. intermediate cavity
D. both (a) and (b)

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Question 41

Assertion (A): The impedance of a matched load is equal to characteristic impedance of line.Reason (R): A matched termination absorbs all the power incident on it.

A. Both A and R are correct and R is correct explanation of A
B. Both A and R are correct but R is not correct explanation of A
C. A is correct but R is wrong
D. A is wrong but R is correct

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Question 42

For a 50 Ω resistor for 3 GHz application, the stray capacitance should be less than

A. 1 μF
B. 1 nF
C. 1 pF
D. 0.1 pF

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Question 43

Assertion (A): A backward wave oscillator has an internal positive feedback.Reason (R): A positive feedback is necessary for sustained oscillations.

A. Both A and R are correct and R is correct explanation of A
B. Both A and R are correct but R is not correct explanation of A
C. A is correct but R is wrong
D. A is wrong but R is correct

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Question 44

Impedance level of Impatt diodes is generally lower than that of Gunn diodes

A. TRUE
B. FALSE

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Question 45

A matched generator (Zg = Z0) with 1 Ω available. If all ports are matched, the power delivered at ports 1, 2, 3 respectively are

A. 0.5 W, 0.5 W, 0 W
B. 0 W, 0 W, 1 W
C. 0.33 W each
D. 0 W, 0.25 W, 0.25 W

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Question 46

In a circular waveguide the dominant mode is

A. TE01
B. TE11
C. TE20
D. TE21

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