Explore topic-wise MCQs in Microwave Engineering.

This section includes 161 Mcqs, each offering curated multiple-choice questions to sharpen your Microwave Engineering knowledge and support exam preparation. Choose a topic below to get started.

1.

(A) The TW tube which is a wideband microwave amplifier of the helix is used as a slow wave structure of the device.(R) The phase velocity of the helix can be profiled along the length of the helix.

A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not a correct explanation of A
C. A is true but R is false
D. A is false but R is true
Answer» B. Both A and R are true but R is not a correct explanation of A
Discussion
2.

(A) The variables choosen for the equivalent circuit of a 2 port network in the microwave range of frequencies are travelling waves rather than total voltage and total currents. (R) In microwave range equipment is not readily available to measure total voltage and total currents at the ports of the networks. Short and open circuits are difficult to achieve over a broad-band of frequencies and active devices frequently will not have stability for a short or open circuit.

A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not a correct explanation of A
C. A is true but R is false
D. A is false but R is true
Answer» B. Both A and R are true but R is not a correct explanation of A
Discussion
3.

(A) In some applications, the TM01 mode in circular waveguide is preferred to the TE01 mode or TE11 mode. (R) TM01 mode not only overcomes the problem of rotation of polarisation in circular waveguide but also requires a smaller diameter.

A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not a correct explanation of A
C. A is true but R is false
D. A is false but R is true
Answer» B. Both A and R are true but R is not a correct explanation of A
Discussion
4.

(A) In an oscillation zone of reflex klystron an increase in the reflector voltage results in lighter oscillation frequency. (R) Electron bunches pass through the interaction gap before the retarding field is at a maximum and an increased reflector voltage results in the induced current lagging in voltage.

A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not a correct explanation of A
C. A is true but R is false
D. A is false but R is true
Answer» C. A is true but R is false
Discussion
5.

A 75 ohm transmission line is first short terminated and the minima locations are noted. When the short is replaced by a resistive load RL, the minima locations are not altered and the VSWR is measured to be 3. What is the value of RL?

A. 25 ohms
B. 50 ohms
C. 1/2
D. 1/4
Answer» C. 1/2
Discussion
6.

A square waveguide carries TE11 mode whose axial magnetic field is given by:Hz = H0cos xcos yA/m 8 8Where the waveguide dimensions are in centimetres. What is the cut-off frequency of the mode?

A. 5 GHz
B. 7 5 GHz
C. 6 5 GHz
D. 8 GHz
Answer» C. 6 5 GHz
Discussion
7.

Fig. shows five thin slots on the walls of a rectangular waveguide carrying TE10 mode. Which of these are radiating (R) and which are non-radiating (NR)?R NRA. D, E A, B, C B. A, B, C D, EC. C, EA, B, D D. B, C, E A, D

A. A
B. B
C. C
D. D
Answer» E.
Discussion
8.

A microwave tube amplifier uses an axial magnetic field and a radial electric field. This is the:

A. Reflex klystron
B. Coaxial magnetron
C. Travelling-wave magnetron
D. CFA
Answer» E.
Discussion
9.

One of the following microwave diodes is suitable for very low-power oscillators only:

A. Tunnel
B. Avalanche
C. Gunn
D. IMPATT
Answer» B. Avalanche
Discussion
10.

A varactor diode may be useful at microwave frequencies (indicate the false answer):

A. For electronic tuning
B. For frequency multiplication
C. As an oscillator
D. As a parametric amplifier
Answer» D. As a parametric amplifier
Discussion
11.

Consider the following statements regarding feed which is the Key component of a reflector antenna as it has a decisive bearing on the overall-performance: 1. For a horn-feed antenna the reflector focus must coincide with horn-feeds phase centre, which for a wide-flare horn lies in the plane of horn aperture. 2. The feed must have minimal radiation outside the angular aperture of reflector. 3. In print focus or cassegrain systems, the main or sub-reflectors should be in Fraunhofer zone of the feed antenna. Which of the statements are correct?

A. 1, 2 and 3
B. 1 and 2
C. 2 and 3
D. 1 and 3
Answer» B. 1 and 2
Discussion
12.

Consider the following statements regarding a cavity wavemeter in a reaction type of circuit as shown in Fig. 1. The distance d is made either zero or approximately a guide half-wave length, so that an effective short circuit appears at the waveguide wall when the cavity is at resonance.2. A dip in the load power occurs as the wavemeter is tuned through resonance.3. The magnitude of the cavity impedance depends only on the distance d. 4. The magnitude of the power dip depends only on the Q of the cavity.

A. 1 alone is correct
B. 2 alone is correct
C. 1 and 3 are correct
D. 2 and 4 are correct
Answer» E.
Discussion
13.

Consider the following statements: In a magic Tee, 1. Collinear arms are isolated from each other. 2. One of the collinear arms is isolated from E-arm. 3. The collinear arms is isolated from H-arm. 4. E-arm and H-arm are isolated from each other of these statements, correct answers are:

A. 1 and 2
B. 1 and 3
C. 1 and 4
D. 2 and 3
Answer» D. 2 and 3
Discussion
14.

In a circular waveguide with radius r , the dominant mode is:

A. TM
B.
C. TE
D. TM
E. TE
Answer» B.
Discussion
15.

The semiconductor diode which can be used in switching circuits at microwave range is:

A. PIN diode
B. Tunnel diode
C. Varactor diode
D. Gunn diode
Answer» B. Tunnel diode
Discussion
16.

Consider the following statements: Laser is an acronym for light amplification by stimulated emission of radiation. In comparison to LED, it has: (i) Higher emission efficiency (ii) No tuning arrangements (iii) Narrow spectral width (iv) Provision for confinement Of the statements:

A. (i), (iii) and (iv) are correct
B. (i), (ii) and (iii) are correct
C. (i) and (iii) are correct
D. (i), (ii) and (iv) are correct
Answer» B. (i), (ii) and (iii) are correct
Discussion
17.

Consider the following statements relating to problem of mounting the bolometer in a waveguide for microwave power measurement. 1. The first requirement in the mounting is that the mount and bolometer match the impedance of the waveguide and this can completely be solved by incorporating tuning elements. 2. The operating resistance of the bolometer, determined by the point of operation may be used as one of the variables in impedance matching and is chosen to be about equal to the characteristic impedance of the waveguide. 3. Mechanically it is very difficult to ensure that the bolometer is subjected to the microwave power and at the same time arranged so that it can be connected in low frequency bridge circuit. 4. A stub and short-circuited section behind the bolometer are introduced for cancelling reflections at frequencies different from the centre frequency and thus to increase the bandwidth of the mount. Of the above statements:

A. 1, 2 and 3 are correct
B. 1, 3 and 4 are correct
C. 2, 3 and 4 are correct
D. 1, 2 and 4 are correct
Answer» E.
Discussion
18.

The skin depth at 1000 MHz, in comparison with that at 500 MHz is:

A. 2
B. 1/
C.
D. 1/2
Answer» D. 1/2
Discussion
19.

A loss-less line having characteristic impedance Z0 is terminated in a pure reactance of value jZ0. The VSWR of the line will be:

A. 10
B. 2
C. 1
D. Infinite
Answer» E.
Discussion
20.

Which of the following statements about parabolic reflector systems are correct? 1. A front-fed shallow parabolic reflector antenna requires a feed horn with narrow radiation pattern relative to that for a deep dish 2. The noise temperature of a Cassegrain system is the highest when it looks at the horizon 3. The noise temperature of a front-fed parabolic antenna is the lowest when it looks at the Zenith 4. The sidelobe level of a parabolic reflector is highest for uniform aperture illumination Select the correct answer using the codes given below:

A. 1, 2 and 3
B. 1, 3 and 4
C. 1, 2 and 4
D. 2, 3 and 4
Answer» D. 2, 3 and 4
Discussion
21.

Consider the following statements associated with microstrip patch antennas: 1. The microstrip patch behaves more like a leaky cavity rather than like a radiator and thus is not is highly efficient antenna. 2. They are broadband antennas and are well suited for mm-waves. 3. They can be adapted for radiation of circularly polarised waves. The correct ones of these statements are:

A. 1, 2 and 3
B. 1 and 2
C. 2 and 3
D. 1 and 3
Answer» C. 2 and 3
Discussion
22.

Indicate the false statement. The advantages of semiconductor lasers over LEDs include:

A. Monochromatic output
B. Higher power output
C. Lower cost
D. Ability to be pulsed at higher rates
Answer» D. Ability to be pulsed at higher rates
Discussion
23.

Communications lasers are used with optical fibres, rather that in open links, to:

A. Ensure that the beam does not spread
B. Prevent atmospheric interference
C. Prevent interference by other lasers
D. Ensure that people are not blinded by them
Answer» C. Prevent interference by other lasers
Discussion
24.

For a given average power, the peak output power of a ruby laser may be increased by:

A. Using cooling
B. Using Q spoiling
C. Increasing the magnetic field
D. Dispensing with the Fabry-Perot resonator
Answer» C. Increasing the magnetic field
Discussion
25.

The output from a laser is monochromatic; this means that it is:

A. Infrared
B. Polarized
C. Narrow-beam
D. Single-frequency
Answer» E.
Discussion
26.

The ruby laser differs from the ruby maser in that the former:

A. Does not require pumping
B. Needs no resonator
C. Is an oscillator
D. Produces much lower powers
Answer» D. Produces much lower powers
Discussion
27.

In order to reduce cross-sectional dimensions, the waveguide to use is:

A. Circular
B. Ridged
C. Rectangular
D. Flexible
Answer» C. Rectangular
Discussion
28.

For best low-level noise performance in the X-band, an amplifier should use:

A. A bipolar transistor
B. A Gunn diode
C. A step-recovery diode
D. An IMPATT diode
Answer» D. An IMPATT diode
Discussion
29.

For low attenuation, the best transmission medium is:

A. Flexible waveguide
B. Ridged waveguide
C. Rectangular waveguide
D. Coaxial line
Answer» D. Coaxial line
Discussion
30.

Indicate which of the following cannot be followed by the word waveguide ?

A. Elliptical
B. Flexible
C. Coaxial
D. Ridged
Answer» D. Ridged
Discussion
31.

For some applications, circular waveguides may be preferred to rectangular ones because of:

A. The smaller cross section needed at any frequency
B. Lower attenuation
C. Freedom from spurious modes
D. Rotation of polarization
Answer» C. Freedom from spurious modes
Discussion
32.

The TWT is sometimes preferred to the multicavity klystron amplifier, because the former:

A. Is more efficient
B. Has a greater bandwidth
C. Has a higher number of modes
D. Produces a higher output power
Answer» C. Has a higher number of modes
Discussion
33.

Indicate the false statement. Transit time in microwave tubes will be reduced if:

A. The electrodes are brought closer together
B. A higher anode current is used
C. Multiple or coaxial leads are used
D. The anode voltage is made larger
Answer» D. The anode voltage is made larger
Discussion
34.

The multicavity klystron:

A. Is not a good low-level amplifier because of noise
B. Has a high repeller voltage to ensure a rapid transit time
C. Is not suitable for pulsed operation
D. Needs a long transit time through the buncher cavity to ensure current modulation
Answer» B. Has a high repeller voltage to ensure a rapid transit time
Discussion
35.

One of the reasons why vacuum tubes eventually fail at microwave frequencies is that their:

A. Noise figure increases
B. Transit time beomes too short
C. Shunt capacitive reactances become too large
D. Series inductive reactances become too small
Answer» B. Transit time beomes too short
Discussion
36.

One of the following is unlikely to be used as a pulsed device. It is the:

A. Multicavity klystron
B. BWO
C. CFA
D. TWT
Answer» C. CFA
Discussion
37.

A microwave tube amplifier uses an axial magnetic field and a radial electric field. This is the:

A. Reflex klystron
B. Coaxial magnetron
C. Travelling-wave magnetron
D. CFA
Answer» E.
Discussion
38.

The transit time in the repeller space of a reflex klystron must be n + 3 4 cycle to ensure that:

A. Electrons are accelerated by the gap voltage on their return
B. Returning electrons give energy to the gap oscillations
C. It is equal to the period of the cavity oscillations
D. The repeller is not damaged by striking electrons
Answer» C. It is equal to the period of the cavity oscillations
Discussion
39.

A magnetic field is used in the cavity magnetron to:

A. Prevent anode current in the absence of oscillations
B. Ensure that the oscillations are pulsed
C. Help in focusing the electron beam, thus preventing spreading
D. Ensure that the electrons will orbit around the cathode
Answer» E.
Discussion
40.

Indicate the false statement. Klystron amplifiers may use intermediate cavities to:

A. Prevent the oscillations that occur in two-cavity klystrons
B. Increase the bandwidth of the device
C. Improve the power gain
D. Increase the efficiency of the klystron
Answer» B. Increase the bandwidth of the device
Discussion
41.

The cavity magnetron uses strapping to:

A. Prevent mode jumping
B. Prevent cathode back-heating
C. Ensure bunching
D. Improve the phase-focusing effect
Answer» B. Prevent cathode back-heating
Discussion
42.

A parametric amplifier must be cooled:

A. Because parametric amplification generates a lot of heat
B. To increase bandwidth
C. Because it cannot operate at room temperature
D. To improve the noise performance
Answer» E.
Discussion
43.

A backward-wave oscillator is based on the:

A. Rising-sun magnetron
B. Crossed-field amplifier
C. Coaxial magnetron
D. Travelling-wave tube
Answer» E.
Discussion
44.

A magnetron whose oscillating frequency is electronically adjustable over a wide range is called a:

A. Coaxial magnetron
B. Dither-tuned magnetron
C. Frequency-agile magnetron
D. VTM
Answer» E.
Discussion
45.

Indicate the false statement. FETs are preferred to bipolar transistors at the highest frequencies because they:

A. Are less noisy
B. Lend themselves more readily to integration
C. Are capable of higher efficiencies
D. Can provide higher gains
Answer» C. Are capable of higher efficiencies
Discussion
46.

The glass tube of a TWT may be coated with aquadag to:

A. Help focusing
B. Provide attenuation
C. Improve bunching
D. Increase gain
Answer» C. Improve bunching
Discussion
47.

Indicate which of the following is not a TWT slow-wave structure?

A. Periodic-permanent magnet
B. Coupled cavity
C. Helix
D. Ring-bar
Answer» B. Coupled cavity
Discussion
48.

Indicate the false statement. An advantage of stripline over microstrip is its:

A. Easier integration with semiconductor devices
B. Lower tendency to radiate
C. Higher isolation between adjacent circuits
D. Higher Q
Answer» B. Lower tendency to radiate
Discussion
49.

Indicate the false statement. An advantage of stripline over waveguides is its:

A. Smaller bulk
B. Greater bandwidth
C. Higher power-handling capability
D. Greater compatibility with solid-state devices
Answer» D. Greater compatibility with solid-state devices
Discussion
50.

The transmission system using two ground planes is:

A. Microstrip
B. Elliptical waveguide
C. Parallel-wire line
D. Stripline
Answer» E.
Discussion