This is the Multiple Choice Questions in Chapter 12: Semiconductor Microwave Devices and Circuits 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. 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
- d. to improve the noise performance temperature
2. A ruby maser amplifier must be cooled
- a. because maser amplification generates a lot of heat
- b. to increase bandwidth
- c. because it cannot operate at room temperature
- d. to improve the noise performance
3. A disadvantage of microstrip compared with stripline is that microstrip
- a. does not readily lend itself to printed circuit techniques
- b. is more likely to radiate
- c. is bulkier
- d. is more expensive and complex to manufacture
4. The transmission system using two ground plane is
- a. microstrip
- b. elliptical waveguide
- c. parallel-wire line
- d. stripline
5. Indicate the false statement. An advantage of stripline over waveguide is its
- a. smaller bulk
- b. greater bandwidth
- c. higher power-handling capability
- d. greater compatibility with solid-state devices
6. 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
7. Surface acoustics waves propagate in
- a. gallium arsenide
- b. indium phosphide
- c. stripline
- d. quartz crystal
8. SAW devices may be used as
- a. transmission media like stripline
- b. filters
- c. UHF amplifiers
- d. Oscillators at millimeter frequencies
9. Indicate the falsestatement. FETs are preferred to bipolar transistors at the highest frequencies because they
- a. are less noisy
- b. lend themselves more easily to integration
- c. are capable of higher efficiencies
- d. can provide higher gains
10. 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
11. The biggest advantage of the TRAPATT diode over the IMPATT diode is its
- a. lower noise
- b. higher efficiency
- c. ability to operator at higher frequencies
- d. lesser sensitivity to harmonics
12. Indicate which of the following diodes will produce the highest pulsed power output:
- a. Varactor
- b. Gunn
- c. Schottky barrier
- d. RIMPATT
13. Indicate which of the following diodes does not use negative resistance in its operation:
- a. Backward
- b. Gunn
- c. IMPATT
- d. Tunnel
14. One of the following is not used as a microwave mixer or detector:
- a. Crystal diode
- b. Schottky-barrier diode
- c. Backward diode
- d. PIN diode
15. One of the following microwave diodes is suitable for very low-power oscillators only:
- a. Tunnel
- b. avalanche
- c. Gunn
- d. IMPATT
16. The transferred-electron bulk effect occurs in
- a. germanium
- b. gallium arsenide
- c. silicon
- d. metal semiconductor junctions
17. The gain-bandwidth frequency of a microwave transistor, fT, is the frequency at which the
- a. alpha of the transistor falls by 3 dB
- b. beta of the transistor falls by 3 dB
- c. power gain of the transistor falls to
- d. beta of the transistor falls to unity unity
18. For a microwave transistor to operate at the highest frequencies, the (indicate the false answer)
- a. collector voltage must be large
- b. collector current must be high
- c. base should be thin
- d. emitter area must be large
19. 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
20. If high-order frequency multiplication is required from a diode multiplier,
- a. the resistive cutoff frequency must be high
- b. a small value of the base resistance is required
- c. a step-recovery diode must be used
- d. a large range of capacitance variation is needed
21. A parametric amplifier has an input and output frequency of 2.25 GHz, and is pumped at 4.5 GHz. It is
- a. traveling-wave amplifier
- b. degenerative amplifier
- c. lower-sideband up-converter
- d. upper-sideband up-converter
22. A non-degenerate parametric amplifier has an input frequency fi and a pump frequency fp. Then idler frequency is
- a. fi
- b. 2fi
- c. fi – fp
- d. fp – fi
23. Traveling-wave parametric amplifiers are used to
- a. provide a greater gain
- b. reduce the number of varactor diodes required
- c. avoid the need for cooling
- d. provide greater bandwidth
24. A parametric amplifier sometimes uses a circulator to
- a. prevent noise feedback
- b. allow the antenna to be used simultaneously for transmission and reception
- c. separate the signal and idler frequencies
- d. permit more efficient pumping
25. The non-degenerate one-port parametric amplifier should have a high ratio of pump to signal frequency because this
- a. permits satisfactory high frequency operation
- b. yields a low noise figure
- c. reduce the pump power required
- d. permits satisfactory
26. The tunnel diode
- a. has a tiny hole through its center to facilitate tunneling
- b. is a point-contact diode with a very high reverse resistance
- c. uses a high doping level to provide a narrow junction
- d. works by quantum tunneling exhibited by gallium arsenide only
27. A tunnel diode is loosely coupled to its cavity in order to
- a. increase the frequency stability
- b. increase the available negative resistance
- c. facilitate tuning
- d. allow operation at the highest frequencies
28. The negative resistance in a tunnel diode
- a. is maximum at the peak point of the characteristic
- b. is available between the peak and valley points
- c. is maximum at the valley point
- d. may be improved by the use of reverse bias
29. The biggest advantage of gallium antimonide over germanium for tunnel diode use it that former has a
- a. lower noise
- b. higher ion mobility
- c. larger voltage swing
- d. simpler fabrication process
30. Negative resistance is obtained with a Gunn diode because of
- a. electron transfer to a less mobile energy level
- b. avalanche breakdown with the high voltage gradient
- c. tunneling across the junction
- d. electron domains forming at the junction
31. For Gunn diodes, gallium arsenide is preferred to silicon because the former
- a. has a suitable empty energy band, which silicon does not have
- b. has a higher ion mobility
- c. has a lower noise at the highest frequencies
- d. is capable of handling higher power densities
32. The biggest disadvantage of the IMPATT diode is its
- a. lower efficiency than that of the other microwave diodes
- b. high noise
- c. inability to provide pulsed operation
- d. low power-handling ability
33. The magnetic field is used with a ruby maser to
- a. provide sharp focusing for the electron beam
- b. increase the population inversion
- c. allow room-temperature operation
- d. provide frequency adjustments
34. The ruby maser has been preferred to the ammonia maser for microwave amplification, because the former has
- a. a much greater bandwidth
- b. a better frequency stability
- c. a lower noise figure
- d. no need for a circulator
35. Parametric amplifiers and masers are similar to each other in that both (indicate false statement)
- a. must have pumping
- b. are extremely low-noise amplifiers
- c. must be cooled down to a few kelvins
- d. generally required circulators, since they are one-port devices
36. A maser RF amplifier is not really suitable for
- a. radio astronomy
- b. satellite communications
- c. radar
- d. troposcatter receiver
37. 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
38. The output from a laser is monochromatic; this means that it is
- a. infrared
- b. polarized
- c. narrow-beam
- d. single-frequency
39. 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
40. Communications lasers are used with optical fiber, rather than in open links, to
- a. ensure that the beam does not spread
- b. prevent atmospheric interference
- c. prevent interference by other laser
- d. ensure that people are not blinded by them
41. 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
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