20:
1103:
The apparent speed for PRF A falls in the 200MPH filter, and the apparent speed for PRF B falls in the 400MPH filter. This combination places the true target speed at 1,400MPH (2x6+2 or 2x5+4). This can be seen graphically when range intervals are stacked end-to-end as shown below.
905:
430:
681:
207:
1035:
700:
222:
479:
59:
53:
Frequency ambiguity resolution is required to obtain the true radial velocity when the measurements is made using a system where the following inequality is true.
911:
1356:
Processing techniques are slightly more complicated when there is more than one reflection at the same distance with slightly different radial velocity.
1373:
1348:
function, where the spectrum amplitudes from one PRF are applied to spectrum samples from the other PRF as a sliding window function.
46:
Radial velocity aliasing occurs when reflections arrive from reflectors moving fast enough for the
Doppler frequency to exceed the
1418:
900:{\displaystyle True\ Velocity=Ambiguous\ Velocity+0.5\times N\left({\frac {PRF\times C}{Transmit\ Frequency}}\right)}
444:, which occurs when the Doppler frequency created by reflector motion exceeds the pulse repetition frequency (PRF).
448:
425:{\displaystyle Apparent\ Velocity=(TrueVelocity)MOD\left({\frac {PRF\times C}{2\times Transmit\ Frequency}}\right)}
47:
31:
1338:"A" represents target speed possibilities for PRF A, and "B" represents target speed possibilities for PRF B.
676:{\displaystyle Ambiguous\ Velocity=-0.5\left({\frac {Doppler\ Frequency\times C}{Transmit\ Frequency}}\right)}
1043:
This is explained best using an example with 2 different PRF, although real systems use a different method.
462:
When the
Doppler frequency shift exceeds the PRF, the frequency is reduced. This limitation is called the
1344:
Ambiguity resolution is typically implemented with a look-up table. This could also be implemented as a
1046:
In the example, PRF A can detect true speed up to 600MPH and PRF B can detect true speed up to 500MPH.
686:
Frequency is folded for high speed targets where radial velocity produces a frequency shift above the
1377:
35:
467:
213:
687:
202:{\displaystyle Radial\ Velocity>0.5\left({\frac {PRF\times C}{Transmit\ Frequency}}\right)}
691:
1341:
This frequency ambiguity resolution signal processing technique determines true velocity.
1398:
1412:
1030:{\displaystyle N=Integer\ Between\pm \left({\frac {0.5\times Bandwidth}{PRF}}\right)}
463:
1345:
454:
Doppler frequency shift is introduced onto reflected signals used by radar.
19:
441:
23:
Doppler signal sampled with a pulse rate near the
Doppler frequency.
18:
1040:
The
Nyquist frequency will also change when the PRF is changed.
212:
The radial velocity measurements made in this way produce a
470:
onto the apparent frequency of the reflected signal.
914:
703:
482:
225:
62:
30:
is used to find the true target velocity for medium
1029:
899:
690:. The true speed of the target may be folded by a
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201:
1376:. Curtin University of Technology. Archived from
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440:Radar pulsing causes a phenomenon called
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61:
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34:(PRF) radar systems. This is used with
473:The ambiguous velocity is as follows.
216:function of the true radial velocity.
7:
694:produced by the sampling process.
14:
319:
280:
28:Frequency ambiguity resolution
1:
447:This concept is related to
1435:
449:range ambiguity resolution
48:pulse repetition frequency
32:pulse repetition frequency
1419:Radar signal processing
1374:"Sampling and Aliasing"
16:Radar signal processing
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901:
677:
426:
203:
24:
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464:Nyquist sampling rate
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466:. This introduces a
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36:pulse-Doppler radar
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688:Nyquist frequency
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1401:. Radartutorial.
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1380:on 2011-07-27
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29:
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1393:
1382:. Retrieved
1378:the original
1368:
1355:
1343:
1340:
1337:
1102:
1095:Target PRF B
1076:Target PRF A
1045:
1042:
1039:
685:
472:
461:
453:
446:
439:
211:
52:
45:
27:
26:
1352:Limitations
1346:convolution
1384:2011-08-03
1360:References
42:Definition
980:×
967:±
829:×
807:×
605:×
541:−
458:Operation
359:×
348:×
131:×
1413:Category
442:aliasing
1067:500MPH
50:(PRF).
1064:400MPH
1061:300MPH
1058:200MPH
1055:100MPH
943:
861:
774:
717:
637:
575:
511:
436:Theory
386:
251:
214:modulo
163:
82:
1052:0MPH
109:>
1197:29
977:0.5
804:0.5
544:0.5
112:0.5
1415::
1332:B
1194:29
1191:27
1188:26
1185:25
1182:24
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1146:12
1143:11
1140:10
451:.
38:.
1387:.
1321:B
1310:B
1299:B
1288:B
1277:B
1258:A
1245:A
1232:A
1219:A
1206:A
1137:9
1134:8
1131:7
1128:6
1125:5
1122:4
1119:3
1116:2
1113:1
1110:0
1024:)
1018:F
1015:R
1012:P
1007:h
1004:t
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971:(
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946:B
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922:I
919:=
916:N
894:)
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744:=
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548:(
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333:(
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281:(
278:=
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116:(
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
