This set of Microwave Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Radar Systems”.
1. In a RADAR system the transmitter of the radar is more sensitive than the receiver.
Explanation: The basic operation of RADAR is that the transmitter sends out a signal, which is partially reflected by the distant target, and then detected by a sensitive receiver. Because of the presence of noise in the received signal, the receiver has to be more sensitive.
2. For radar system, antennas with a large beam width are preferred over narrow beam antennas.
Explanation: If a narrow beam width antenna is used in radar, the target’s direction can be accurately given by the angular position of the antenna. Hence narrow beam antennas give more accurate position of the objects.
3. The radar in which both transmission and reception is done using the same antenna are called:
a) Monostatic radar
b) Bistatic radar
c) Monopole radar
d) Dipole radar
Explanation: Radar transmits electromagnetic waves and receives the waves that are reflected by objects. If a single antenna is used both for transmission and reception of the signals, they are called monostatic radar.
4. For applications like missile fire control, bistatic radars are used.
Explanation: In missile fire control, the target is illuminated with one antenna and the reflected wave is received from another antenna in the radar. In situations where continuous transmission and reception of signals is required, bistatic radars are used.
5. When a power Pt is transmitted by an antenna, amount of energy incident on the target is given by the expression:
c) Pt×4 πR2/G
d) None of the mentioned
Explanation: The amount of energy incident on the target is proportional to the energy radiated; gain of the antenna G, and R is the distance of the target from the radar system. As the distance from the radar system, the energy incident on the target reduces.
6. The term radar cross section defines the:
a) Scattering ability of the target
b) Power radiating ability of the radar
c) Amount of energy scattered by unwanted objects
d) Cross section of radar area through which energy is emitted
Explanation: Radar cross section is defined as the ratio of scattered power in a given direction to the power incident on it. The power incident is the energy radiated by the transmitting antenna of the radar.
7. A ________ determines the target range by measuring the round trip time of a pulsed microwave signal.
a) Pulse radar
b) Doppler radar
c) Cross section radar
d) None of the mentioned
Explanation: The working principle of pulse radar is that continuous pulses are transmitted and time is recorded until the pulse is received back by the radar. Based on this delay recorded, the range of target is estimated.
8. Construction of pulse radar is much simpler than a Doppler radar.
Explanation: In Doppler radar the power / signal is continuously radiated by the transmitting antenna. In pulse radar, pulses are transmitted to the target. Generation and transmission of pulses is more complex as compared to continuous signal.
9. In military applications the radar cross sections of vehicles is minimized.
Explanation: In military applications the radar cross sections of vehicles is minimized so that the military vehicles remain undetected. Lower the radar cross section, lower is the power scattered, and hence the object remains undetected.
10. Pulse radar operating at 10GHz frequency has an antenna with a gain of 28 dB and a transmitted power of 2kW. If it is desired to detect a target of cross section 12m2, and the minimum detectable signal is -90 dBm, the maximum range of the radar is:
a) 8114 m
b) 2348 m
c) 1256 m
d) 4563 m
Explanation: The maximum range of a radar system is given the expression, [PtG2σλ22/ (4π) Pmin] 0.25. Pt is the transmitted power, σ is the radar cross section, G is the antenna gain. Substituting the given values in the above equation, the maximum range of the radar is 8114 m.
Sanfoundry Global Education & Learning Series – Microwave Engineering.
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