This set of Radar Multiple Choice Questions & Answers (MCQs) focuses on “Staggered Pulse Repetition Frequency”.
1. What is the use of multiple waveforms with different pulse repetition frequencies?
a) To increase the strength of target signal
b) To detect moving targets
c) To allow faster transmission
d) To reduce clutter
View Answer
Explanation: Using multiple waveforms with different pulse repetition frequencies is one of the best methods in order to detect a target because if we don’t use changing PRF waveform then it’ll be removed if their radial velocities were in the range of the blind speed.
2. Which out of the following is not a valid method for employing multiple PRFs to avoid losing target echoes due to blind speeds?
a) Scan to scan
b) Dwell to dwell
c) Pulse to pulse
d) Target to target
View Answer
Explanation: Scan to scan, dwell to dwell and pulse to pulse are methods for employing multiple PRFs to avoid losing target echoes due to blind speeds. A dwell is the time on target and is usually the time it takes to scan the antenna beam over a beam width or some fraction of a beam width.
3. In pulse-to-pulse staggered PRFs, the time between pulses is in an interval or a ________
a) period
b) duration
c) frequency
d) velocity
View Answer
Explanation: In pulse-to-pulse staggered PRFs, the time between pulses is in an interval or a period. The term interval is more appropriate, but the term period arose historically and its use remains even though it might not always be used precisely.
4. The null depth depends mainly on the ratio of the maximum-to-minimum period.
a) True
b) False
View Answer
Explanation: The null depth depends mainly on the ratio of the maximum-to-minimum period. The depth of the deepest null within the MTI filter pass band when using a staggered waveform found by Shrader based on computer search for the best sets of pulse periods.
5. How many methods are there to find the effect of the stagger periods on the depth of the null and the MTI improvement factor?
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: There have been two methods proposed for finding the effect of the stagger periods on the depth of the null and the MTI improvement factor which are computer search and analytic formulation. There have been other methods too but some of them are concerned mainly with minimizing the extent of the deepest null and do not examine the effect on the improvement factor.
6. Which out of the following is the correct formula for maximum improvement factor?
a) Imax = 1 / 2π2σc2σn
b) Imax = 1 / 4π2σcσn2
c) Imax = 1 / 2π2σc2σn2
d) Imax = 1 / 4π2σc2σn2
View Answer
Explanation: The correct formula for maximum improvement factor Imax = 1 / 4π2σc2σn2 where σc2 = total variance of a Gaussian clutter spectrum, σn2 = mean square value of ϵn = Ti – Tav, Ti = period of the ith stagger, and Tav = average value of the n periods.
7. Which out of the following staggering technique along with several pulse periods can significantly increase the blind speed compared to a constant PRF waveform?
a) Dwell-to-Dwell
b) Pulse-to-pulse
c) Scan-to-scan
d) Period-to-period
View Answer
Explanation: Pulse-to-pulse stagger with several pulse periods and can significantly increase the blind speed compared to a constant PRF waveform and it doesn’t have large regions of Doppler space where moving targets are not detected as, for example when a double or triple delay-line canceler is used.
8. Compared to recursive filters, staggered PRF filter design is ___________
a) simplified
b) complex
c) same
d) null
View Answer
Explanation: Compared to recursive filters, staggered PRF filter design is simplified since it does not require the feedback found in recursive filters nor does it experience poor transient response, not to mention staggered PRF can attain improvement in low frequency cutoff and smoothness.
9. Staggering the PRFs slightly degrades the improvement factor.
a) True
b) False
View Answer
Explanation: Staggering the PRFs slightly degrades the improvement factor by transferring clutter energy to the Doppler frequency space and is more difficult to stabilize a transmitter that doesn’t have a constant PRF. Also, it does not cancel multiple-time-around clutter.
10. The radar that changes its PRF from scan to scan is easier to implement and it can cancel __________
a) ambiguous clutter
b) echo clutter
c) second time around clutter
d) multiple time around clutter
View Answer
Explanation: The radar that changes its PRF from scan to scan is easier to implement and it can cancel multiple time around clutter. Seldom would more than two different PRFs be used to unmask blind speeds in a scan to scan staggered system. With only two PRFs, the reduction in blind speeds is not as effective as when many periods are employed, as in a staggered waveform.
Sanfoundry Global Education & Learning Series – Radar.
To practice all areas of Radar, here is complete set of Multiple Choice Questions and Answers.
