This set of Radar Multiple Choice Questions & Answers (MCQs) focuses on “Solid State RF Power Sources”.
1. In case of a single microwave transistor, the lower the frequency the greater can be the _________
a) power
b) current
c) voltage
d) noise
View Answer
Explanation: For a single microwave transistor, the lower the frequency the greater can be the power. To increase the power, transistors may be operated in parallel, and with more than one stage to increase the gain.
2. Who hypnotized “a microwave transistor capable of perhaps 50 W average power cannot handle much more than 100 to 200 W of peak power without overheating during the pulse”?
a) E. Kreyszig
b) Borkowski
c) R.P. Feynman
d) K.R. Demarest
View Answer
Explanation: It was Borkowski. According to the hypothesis, solid state amplifiers for radar generally operate in the vicinity of 0.1 duty factor, instead of 0.001 to 0.01 duty factors common with high power vacuum tube RF power sources. Thus when solid state devices are employed in radar transmitters they have long pulse widths and require pulse compression to obtain useful range resolution.
3. When the radar waveform is of low power and of high duty cycle, which device is used as a direct replacement for a vacuum tube?
a) Low power output device
b) High tensile device
c) Solid state device
d) High power output device
View Answer
Explanation: Solid state device is used as a direct replacement for a vacuum tube. Examples are the FM-CW radar altimeter, Doppler (police) speed meter, and the airborne Doppler navigator. The solid state transmitter has been highly successful in such applications.
4. Which was the first solid state radar to have its tube transmitter replaced by solid state?
a) Flycatcher
b) TRML-3D/32
c) Sindre II
d) AN/SPS-40
View Answer
Explanation: The first solid state radar to have its tube transmitter replaced by solid state was the AN/SPS-40, modest UHF 2D shipboard air-surveillance radar used mainly by United States ASW (antisubmarine warfare) destroyers to provide conventional air surveillance for keeping track of ASW aircraft.
5. What is the full form of RAMP?
a) Radar Modernization Project
b) Radar Miniaturizing Protocol
c) Radar Maximizing Project
d) Radar Maintenance Protocol
View Answer
Explanation: The RAMP (Radar Modernization Project) radar system was an L-band (1250 to 1350 MHz) air traffic control Primary Surveillance Radar (PSR) located at major airports across Canada. It was developed by Raytheon Canada and had a range of 80 nmi and an altitude coverage of 23,000 ft against a 2 m2 aircraft target with 80 percent probability of detection.
6. How many modules were used in the RAMP Primary Surveillance Radar?
a) 13
b) 14
c) 15
d) 16
View Answer
Explanation: There were a total of 14 modules used in the RAMP PSR. Each module consisted of 42 identical class C 100 W peak power silicon bipolar transistors arranged in a 2-8-32 configuration to produce 2350 W of peak power. The 14 modules were combined as pairs to form seven transmitting channels.
7. In a T/R module used for an active-aperture phased array radar, which device obtains a beam steering command from a central computer and calculates the correct settings for the phase shifter?
a) Driver amplifier
b) Phase shifter
c) Module controller
d) Circulator
View Answer
Explanation: Module controller obtains a beam steering command from a central computer and calculates the correct settings for the phase shifter. To minimize power consumption, the power amplifiers and the LNA might be gated off when the controller is on. The module controller might also perform self-testing and reporting of the status of the module.
8. Which one out of the following is a UHF radar developed by Raytheon that was the first all solid state active aperture electronically steered phased array radar?
a) RP-21 Sapfir
b) Type 571 Radar
c) JY-17 Radar
d) AN/FPS-115
View Answer
Explanation: AN/FPS-115 is a UHF radar developed by Raytheon that was the first all solid state active aperture electronically steered phased array radar. Its function was to detect and warn of sea-launched ballistic missiles fired at the United States. It operated from 420 to 450 MHz with a peak power of 600 kW and an average power of 150 kW, which corresponds to a duty cycle of 0.25.
9. The power output of the silicon bipolar transistor decreases with increasing frequency.
a) True
b) False
View Answer
Explanation: It is true since at higher microwave frequencies, the gallium arsenide FET, often in the form of a MESFET (metal semiconductor field-effect transistor) is capable of greater power than the silicon bipolar transistor and transistors should be operated at a high duty cycle.
10. Power vacuum tubes are well suited for low duty cycles.
a) True
b) False
View Answer
Explanation: It is true since for a given average power their peak power can be increased by a factor of 1000 or more with little penalty other than the practical problem of making the insulators able to stand off the higher voltages. Semiconductor power devices, on the other hand, cannot be efficiently operated at low duty cycles.
Sanfoundry Global Education & Learning Series – Radar.
To practice all areas of Radar, here is complete set of Multiple Choice Questions and Answers.
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