# Kennedy: MCQs in Waveguides, Resonators and Components

(Last Updated On: December 8, 2017)

This is the Multiple Choice Questions in Chapter 10: Waveguides, Resonators and Components from the book Electronic Communication Systems by George Kennedy. If you are looking for a reviewer in Communications Engineering this will definitely help. I can assure you that this will be a great help in reviewing the book in preparation for your Board Exam. Make sure to familiarize each and every questions to increase the chance of passing the ECE Board Exam.

### Start Practice Exam Test Questions

Choose the letter of the best answer in each questions.

1. When an electromagnetic waves are propagated in a waveguide

• a. they travel along a broader walls of the guide
• b. they are reflected from the walls but do not travel along them
• c. they travel through the dielectric without touching the walls
• d. they travel along all four walls of the waveguide

2. Waveguides are used mainly for microwave signals because

• a. they depend on straight-line propagation which applies to microwaves only
• b. losses would be too heavy at lower frequencies
• c. there are no generators powerful enough to excite them at lower frequencies
• d. they would be too bulky at lower frequencies

3. The wavelength of a wave in a waveguide

• a. is greater than of free space
• b. depends only on the waveguide dimensions and the free-space wavelength
• c. is inversely proportional to the phase velocity
• d. is directly proportional to the group velocity

4. The main difference between the operation of transmission lines and waveguides is that

• a. the latter are not distributed, like transmission lines
• b. the former can use stubs and quarter-wave transformers, unlike the latter
• c. transmission lines use the principal mode of propagation, and therefore do not suffer from low-frequency cut-off
• d. terms such as impedance matching and standing-wave ratio cannot be applied to waveguides

5. Compared with equivalent transmission lines, 3-GHz waveguides (indicate false statement)

• a. are less lossy
• b. can carry higher powers
• c. are less bulky
• d. have lower attenuation

6. When a particular mode is excited in a waveguide, three appears an extra electric component, in the direction of propagation. The resulting mode is

• a. transverse-electric
• b. transverse-magnetic
• c. longitudinal
• d. transverse-electromagnetic

7. When electromagnetic waves are reflected at an angle from a wall, their wavelength along the wall is

• a. the same as in free space
• b. the same as the wavelength perpendicular to the wall
• c. shortened because of Doppler effect
• d. greater than in the actual direction of propagation

8. As a result of reflections from a plane conducting wall, electromagnetic waves acquire an apparent velocity greater than the velocity of light in space. This is called the

• a. velocity of propagation
• b. normal velocity
• c. group velocity
• d. phase velocity

9. Indicate the false statement. When the free space wavelength of a signal equals the cut-off wavelength of the guide

• a. the group velocity of the signal becomes zero
• b. the phase velocity of the signal becomes infinite
• c. the characteristic impedance of the guide becomes infinite
• d. the wavelength within the waveguide becomes infinite

10. A signal propagation in a waveguide has a full wave of electric intensity change between the two further walls, and no component of the electric field in the direction of propagation. The mode is

• a. TE1,1
• b. TE1,0
• c. TM2,2
• d. TE2,0

11. The dominant mode of propagation is preferred with rectangular waveguides because (indicate false statement)

• a. it leads to the smallest waveguide dimensions
• b. the resulting impedance can be matched directly to coaxial lines
• c. it is easier than the other modes
• d. propagation of it without any spurious generation can be ensured

12. A choke flange may be used to couple two waveguides

• a. to help in the alignment of the waveguides
• b. because it is simpler than any other join
• c. to compensate for discontinuities at the join
• d. to increase the bandwidth of the system

13. In order to couple two generators to a waveguide system without coupling them to each other, on could not use a

• a. rat-race
• b. E-plane T
• c. hybrid ring
• d. magic T

14. Which of the following waveguides tuning components is not easily adjustable?

• a. Screw
• b. Stub
• c. Iris
• d. Plunger

15. A piston attenuator is a

• a. vane attenuator
• b. waveguide below cutoff
• c. mode filter
• d. flap attenuator

16. Cylindrical cavity resonators are not used with klystrons because they have

• a. a Q that is too low
• b. a shape whose resonant frequency is too difficult to calculate
• c. harmonically related resonant frequencies
• d. too heavy losses

17. A directional coupler with three or more holes is sometimes used in preference to the two-hole coupler

• a. because it is more efficient
• b. to increase coupling of the signal
• c. to reduce spurious mode generation
• d. to increase the bandwidth of the system

18. A ferrite is

• a. a nonconductive with magnetic properties
• b. an intermetallic compound with particularly good conductivity
• c. an insulator which heavily attenuates magnetic fields
• d. a microwave semiconductor invented by Faraday

19. Manganese ferrite may be used as a (indicate false answer)

• a. circulator
• b. isolator
• c. garnet
• d. phase shifter

20. The maximum power that may be handled by a ferrite component is limited by the

• a. Curie temperature
• b. Saturation magnetization
• c. line width
• d. gyromagnetic resonance

21. A PIN diode is

• a. a metal semiconductor point-contact diode
• b. a microwave mixer diode
• c. often used as a microwave detector
• d. suitable for use as a microwave switch

22. A duplexer is used

• a. to couple two different antennas to a transmitter without mutual interference
• b. to allow the one antenna to be used for reception or retransmission without mutual interference
• c. to prevent interference between two antennas when they are connected to a receiver
• d. to increase the speed of the pulses in pulses in pulsed radar

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

• a. the smaller cross
• b. lower attenuation
• section needed at any frequency
• c. freedom from spurious modes
• d. rotation of polarization

24. Indicate which of the following cannot be followed by the word “waveguide”:

• a. Elliptical
• b. Flexible
• c. Coaxial
• d. Ridged

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

• a. circular
• b. ridged
• c. rectangular
• d. flexible

26. For low attenuation, the best transmission medium is

• a. flexible waveguide
• b. ridged waveguide
• c. rectangular waveguide
• d. coaxial line