This set of Radar Multiple Choice Questions & Answers (MCQs) focuses on “Integration of Radar Pulses”.
1. The number of pulses returned from a point target by a scanning a radar is called as _______
a) hits per scan
b) power per scan
c) scanned pulses
d) variable pulses
View Answer
Explanation: Hits per scan or scan per pulses is the number of pulses returned from a point target by a scanning radar with pulse repetition frequency fp Hz, antenna beam width of θB degrees, and scans at a rate of θS degrees per second.
2. What does ωr stands for in the equation, n = θB fp / 6 ωr?
a) Revolutions per phase
b) Revolutions per frequency
c) Revolutions per second
d) Revolutions per minute
View Answer
Explanation: In the above equation, ωr stands for revolutions per minute (rpm) of a 360° rotating antenna where n stands for pulses per scan. Rpm is nothing but a term used to indicate the speed of something saying how many times it is going to revolve in a circle per minute.
3. The process of summing all the radar echoes available from a target is known as a differentiator.
a) True
b) False
View Answer
Explanation: Integrator is the process of adding all the radar echoes available from a target. One of the benefits of using the integration method was to take advantage of the persistence of phosphor of the CRT mixed with integrating features of eye and brain of radar operator, but these days they are replaced by digital methods.
4. What is the integration performed in the radar receiver before the second detector called as?
a) Postdetection Integration
b) Predetection Integration
c) Second Integration
d) Noncoherent integration
View Answer
Explanation: Predetection integration is the integration performed in the radar receiver before the second detector. Even though it is theoretically lossless, it still requires the knowledge of echo signal pulses and preserve it in order to merge sine wave pulses in phase with no loss.
5. Why is it easier to accomplish coherent integration over noncoherent integration?
a) No integration loss
b) Phases of echoes are preserved
c) Only envelopes need to be aligned
d) Higher signal to noise ratio
View Answer
Explanation: Postdetection or coherent integration is easier to accomplish compared to predetection or coherent detection because of two major reasons. Firstly, it doesn’t require to preserve the phases of echoes and secondly, only the envelopes of the pulses need to be aligned to perform addition.
6. What is the crucial reason behind loss in integration efficiency?
a) High percentage of integration loss
b) Nonlinear action of second detector
c) Probability of the appearance false alarm
d) Higher pulse scan rate
View Answer
Explanation: The loss is caused by nonlinear behavior of second detector. If the n pulses present in SNR are integrated with ideal postedetection device, the resultant SNR would be less than n times of that of a single pulse. Therefore, second detector converts the signal energy to noise energy in the process called as rectification.
7. The improvement in signal to noise ratio when n pulses are integrated is called as _______
a) SNR improvement factor
b) Pulse improvement factor
c) Power improvement factor
d) Integration improvement factor
View Answer
Explanation: Integration improvement factor is the improvement in signal to noise when n number of pulses are integrated. It is represented by Ii = nEi(n) or neq = nEi(n) where for post integration, neq is less than n, and as for ideal predetection integration, neq = n.
8. Who defined integration loss in dB and used the false alarm number nf instead of the probability of false alarm?
a) J. I. Marcum
b) R. A. Campbell
c) Rodrigue
d) Wurtz
View Answer
Explanation: It was Marcum who defined integration loss in dB as Li(n) = 10log[1/Ei(n)]. When the integration loss and the integration improvement factor were plotted, it was noticed that they varied only slightly with probability of detection or probability of false alarm, not to mention his false alarm number was the reciprocal of false alarm probability.
9. When n pulses are integrated in radar, there will be lower rate of making detection decisions.
a) True
b) False
View Answer
Explanation: When n pulses are integrated in radar, it does not mean that there will be more false alarm but the rate will get lower for detection decisions. This is one of the reason why false alarm probability is not good compared to a descriptor of false alarms.
10. What happens when a large number of pulses are integrated at the perfect lossless predetection integrator line in the plot between Integration-Improvement factor?
a) Similarity between predetection and postdetection gets less articulated
b) Difference between predetection and postdetection gets more articulated
c) Similarity between predetection and postdetection gets more articulated
d) Difference between predetection and postdetection gets less articulated
View Answer
Explanation: When a large number of pulses are integrated or when we get small signal to noise ratio per pulse, the difference between predetection and postdetection integration gets more pronounced or clear compared to the time when few pulses are integrated and the performances of both of them are not much different.
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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