MCQOPTIONS
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MCQOPTIONS
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.
| 51. |
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 |
| Answer» C. Is bulkier | |
| 52. |
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 |
| Answer» D. To improve the noise performance | |
| 53. |
The biggest advantage of the TRAPATT diode over the IMPATT diode is its: |
| A. | Lower noise |
| B. | Higher efficiency |
| C. | Ability to operate at higher frequencies |
| D. | Lesser sensitivity to harmonics |
| Answer» C. Ability to operate at higher frequencies | |
| 54. |
The transferred-electron bulk effect occurs in: |
| A. | Germanium |
| B. | Gallium arsenide |
| C. | Silicon |
| D. | Metal semiconductor junctions |
| Answer» C. Silicon | |
| 55. |
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 | |
| 56. |
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 |
| Answer» E. | |
| 57. |
Indicate which of the following diodes does not use negative resistance in its operation? |
| A. | Backward |
| B. | Gunn |
| C. | IMPATT |
| D. | Tunnel |
| Answer» B. Gunn | |
| 58. |
Indicate which of the following diodes will produce the highest pulsed power output? |
| A. | Varactor |
| B. | Gunn |
| C. | Schottky barrier |
| D. | RIMPATT |
| Answer» E. | |
| 59. |
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 |
| Answer» B. Saturation magnetization | |
| 60. |
A parametric amplifier has an input and output frequency of 2 25 GHz, and is pumped at 4 5 GHz. It is a: |
| A. | Travelling-wave amplifier |
| B. | Degenerate amplifier |
| C. | Lower-sideband up-converter |
| D. | Upper-sideband up-converter |
| Answer» C. Lower-sideband up-converter | |
| 61. |
If high-order frequency multiplication is required from a diode multiplier: |
| A. | The resistive cutoff frequency must be high |
| B. | A small value of base resistance is required |
| C. | A step-recovery diode must be used |
| D. | A large range of capacitance variation is needed |
| Answer» D. A large range of capacitance variation is needed | |
| 62. |
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 | |
| 63. |
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 |
| Answer» E. | |
| 64. |
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 |
| Answer» B. Has a higher ion mobility | |
| 65. |
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 |
| Answer» B. Avalanche breakdown with the high-voltage gradient | |
| 66. |
A maser RF amplifier is not really suitable for: |
| A. | Radioastronomy |
| B. | Satellite communications |
| C. | Radar |
| D. | Troposcatter receivers |
| Answer» D. Troposcatter receivers | |
| 67. |
Parametric amplifiers and masers are similar to each other in that both (indicate false statement): |
| A. | Must have pumping |
| B. | |
| C. | Are extremely low-noise amplifiers |
| D. | Must be cooled down to a few kelvins |
| E. | Generally require circulators, since they are one-port devices |
| Answer» D. Must be cooled down to a few kelvins | |
| 68. |
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 |
| Answer» B. A better frequency stability | |
| 69. |
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 adjustment |
| Answer» E. | |
| 70. |
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 |
| Answer» C. Inability to provide pulsed operation | |
| 71. |
SAW devices may be used as: |
| A. | Transmission media like stripline |
| B. | Filters |
| C. | UHF amplifiers |
| D. | Oscillators at millimeter frequencies |
| Answer» C. UHF amplifiers | |
| 72. |
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 |
| Answer» E. | |
| 73. |
The biggest advantage of gallium antimonide over germanium for tunnel-diode use is that the former has a: |
| A. | Lower noise |
| B. | Higher ion mobility |
| C. | Larger voltage swing |
| D. | Simpler fabrication process |
| Answer» D. Simpler fabrication process | |
| 74. |
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 |
| Answer» C. Is maximum at the valley point | |
| 75. |
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 |
| Answer» B. Increase the available negative resistance | |
| 76. |
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 unity |
| D. | Beta of the transistor falls to unity |
| Answer» E. | |
| 77. |
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. | Reduces the pump power required |
| D. | Permits satisfactory low-frequency operation |
| Answer» C. Reduces the pump power required | |
| 78. |
A parametric amplifier sometimes uses a circular 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 |
| Answer» B. Allow the antenna to be used simultaneously for transmission and reception | |
| 79. |
Travelling-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 a greater bandwidth |
| Answer» E. | |
| 80. |
Surface acoustic waves propagate in: |
| A. | Gallium arsenide |
| B. | Indium phosphide |
| C. | Stripline |
| D. | Quartz crystal |
| Answer» E. | |
| 81. |
The tunnel diode: |
| A. | Has a tiny hole through its centre 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 |
| Answer» D. Works by quantum tunneling exhibited by gallium arsenide only | |
| 82. |
The TWT is sometimes preferred to the magnetron as a rader transmitter output tube because it is: |
| A. | Capable of a longer duty cycle |
| B. | A more efficient amplifier |
| C. | More broadband |
| D. | Less noisy |
| Answer» B. A more efficient amplifier | |
| 83. |
Periodic permanent-magnet focusing is used with TWTs to: |
| A. | Allow pulsed operation |
| B. | Improve electron bunching |
| C. | Avoid the bulk of an electromagnet |
| D. | Allow coupled-cavity operation at the highest frequencies |
| Answer» D. Allow coupled-cavity operation at the highest frequencies | |
| 84. |
The attenuator is used in the travelling-wave tube to: |
| A. | Help bunching |
| B. | Prevent oscillations |
| C. | Prevent saturation |
| D. | Increase gain |
| Answer» C. Prevent saturation | |
| 85. |
The primary purpose of the helix in a travelling-wave tube is to: |
| A. | Prevent the electron beam from spreading in the long tube |
| B. | Reduce the axial velocity of the RF field |
| C. | Ensure broadband operation |
| D. | Reduce the noise figure |
| Answer» C. Ensure broadband operation | |
| 86. |
To avoid difficulties with strapping at high frequencies, the type of cavity structure used in the magnetron is the: |
| A. | Hole-and-slot |
| B. | Slot |
| C. | Vane |
| D. | Rising-sun |
| Answer» E. | |
| 87. |
Manganese ferrite may be used as a (indicate false answer): |
| A. | Circulator |
| B. | Isolator |
| C. | Garnet |
| D. | Phase shifter |
| Answer» D. Phase shifter | |
| 88. |
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 |
| Answer» E. | |
| 89. |
Short term fading in microwave communication links can be overcome by: |
| A. | Increasing the transmitted power |
| B. | Changing the antenna |
| C. | Changing the modulation scheme |
| D. | Diversity reception and transmission |
| Answer» E. | |
| 90. |
The front end of an amplifier chain in manufacture of communication system is kept immersed in liquid nitrogen, to: |
| A. | Dissipate heat generated by amplifier |
| B. | Expand its frequency response |
| C. | Improve its noise figure |
| D. | Reduce the distortion by the amplifier |
| Answer» C. Improve its noise figure | |
| 91. |
In microwave we take the elements as: |
| A. | Lumped circuit element |
| B. | Distributed circuit element |
| C. | Both (a) and (b) above |
| D. | None of the above |
| Answer» C. Both (a) and (b) above | |
| 92. |
The main advantage of the two hole directional coupler is: |
| A. | Low directional coupling |
| B. | High SWR |
| C. | Poor directivity |
| D. | Narrow bandwidth |
| Answer» E. | |
| 93. |
For a directional coupler the power is in the range of: |
| A. | 40 dB |
| B. | 30 dB |
| C. | 20 dB |
| D. | 10 dB |
| Answer» D. 10 dB | |
| 94. |
Most of the power measuring microwave devices measure: |
| A. | Average power |
| B. | Peak power |
| C. | Instantaneous power |
| D. | None of these |
| Answer» B. Peak power | |
| 95. |
In comparison to an unloaded cavity, value of factor of a loaded cavity is: |
| A. | Higher |
| B. | Lower |
| C. | Same |
| D. | None of these |
| Answer» C. Same | |
| 96. |
Which of the following is directly measured in sweep reflectometry? |
| A. | SWR |
| B. | Impedance |
| C. | Reflection Coefficient |
| D. | Return loss |
| Answer» E. | |
| 97. |
A PIN diode is suitable for use as a: |
| A. | Microwave switch |
| B. | Microwave mixed diode |
| C. | Microwave detector |
| D. | None of these |
| Answer» B. Microwave mixed diode | |
| 98. |
A magic-tee is nothing but: |
| A. | A modification of E-plane tee |
| B. | A modification of H-plane tee |
| C. | A combination of E-plane and H-plane tee |
| D. | Two E-plane tees connected in parallel |
| Answer» D. Two E-plane tees connected in parallel | |
| 99. |
Rain drop attenuation in most microwave communication links is caused due to: |
| A. | Scattering of microwaves by water drops of specific size |
| B. | Scattering of microwaves by a collection of droplets acting as a single body |
| C. | Absorption of microwave by water and consequent heating of the liquid |
| D. | Absorption of microwaves by water-vapour in the atmosphere |
| Answer» E. | |
| 100. |
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 | |