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
The fabrication of microstrip line is done by
A. photo etching
B. printed circuit technique
C. oxidation
D. cladding
Question 2
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
Question 3
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)
Question 4
Skin effect is more pronounced at high frequencies.
A. TRUE
B. FALSE
Question 5
The action of backward wave oscillator is similar to that of
A. klystron amplifier
B. reflex klystron oscillator
C. TWT
D. magnetron
Question 6
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°
Question 7
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)
Question 8
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
Question 9
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
Question 10
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
Question 11
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
Question 12
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
Question 13
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
Question 14
In a backward wave oscillator the wave travelling along the line winds itself back and forth
A. TRUE
B. FALSE
Question 15
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
Question 16
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
Question 17
Which TM mode in rectangular waveguide has lowest cutoff frequency?
A. TM11
B. TM01
C. TM10
D. TM21
Question 18
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
Question 19
Which of the following parameters is negligible in transmission lines?
A. R
B. L
C. C
D. G
Question 20
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
Question 21
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)
Question 22
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
Question 23
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
Question 24
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
Question 25
Impedance level of Impatt diodes is generally lower than that of Gunn diodes
A. TRUE
B. FALSE
Question 26
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
Question 27
Which of the following devices uses a helix?
A. Klystron amplifier
B. Klystron oscillator
C. TWT
D. Both (a) and (b)
Question 28
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
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
Question 30
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
Question 31
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
Question 32
In a travelling wave tube distributed interaction between an electron beam and a travelling wave takes place
A. TRUE
B. FALSE
Question 33
In a klystron amplifier the input cavity is called
A. buncher
B. catcher
C. Pierce gun
D. collector
Question 34
Reflex klystron oscillator is essentially a low power device
A. TRUE
B. FALSE
Question 35
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
Question 36
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)
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
Question 38
A waveguide section in a microwave circuit acts as
A. LP filter
B. Bandpass filter
C. HP filter
D. Band stop filter
Question 39
Which of the following lines is non-radiating?
A. Open two wire
B. Coaxial
C. Both
D. None of the above
Question 40
In a microstrip transmission the signal can be easily redirected by changing the centre strip.
A. TRUE
B. FALSE
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
Question 42
Microwave resonators are used in
A. microwave oscillators
B. microwave narrow band amplifier
C. microwave frequency metres
D. all of the above
Question 43
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
Question 44
Both Impatt and Trapatt devices use avalanche effect
A. TRUE
B. FALSE
Question 45
In a circular waveguide the dominant mode is
A. TE01
B. TE11
C. TE20
D. TE21
Question 46
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