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Coherent demodulation\detection is usually done via matched filtering in RF signal processing. In radar signals, coherent integration can be done if the phases of the returns are known. In terms of coherent detection in radar signals, does it make any sense if we still use matched filtering, similarly to RF signals? Or, coherent detection means coherent integration in radar signals?

I am new to radar signal processing and trying to clarify some concepts here.

Thanks.

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  • $\begingroup$ Matched filtering is coherent integration; they are not two separate things. $\endgroup$ – Dan Boschen Apr 9 at 11:25
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In the context of wireless systems, coherent detection has the definition of detection when the wireless channel is known at the receiver and thus matched filtering is possible and infact optimal at low SNR.

The signals from different antennas at the radar receiver are coherently combined using maximum ratio combining. The MRC is nothing but the matched filter.

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Coherent demodulation\detection is usually done via matched filtering in RF signal processing

No, that's not generally true:

  1. Matched filtering only is an optimal technique if you want to maximize SNR in an AW(G)N channel
  2. In many, if not most, systems that do matched filtering, that matched filter is realized in baseband, i.e. after coherent demodulation. True matched filters in passband are pretty nontrivial to realize!

Coherent demodulation means you know the frequency and phase of your transmitter exactly at your transceiver.

In radar signals, coherent integration can be done if the phases of the returns are known.

Exactly!

In terms of coherent detection in radar signals, does it make any sense if we still use matched filtering, similarly to RF signals?

Yes, if, and only if, you've got uncorrelated additive noise.

Or, coherent detection means coherent integration in radar signals?

The first is a requirement for the second, I'd say, but not the same.

Notice that matched filtering followed by sampling is essentially a correlation, which is an integral over the pulse shape – so it'd be fair to say that "with a coherent detector, feeding a synchronously sampled matched filter, you build a coherent integrator, giving you the maximum SNR in AWGN channels".

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  • $\begingroup$ I think your explanation on radar signals might be true. However, I couldn't agree with you completely on the radio signal portion. $\endgroup$ – Cindy Apr 8 at 12:59
  • $\begingroup$ I think OP meant processing of radio communication signals which doesn’t preclude processing at baseband when “RF Signal Processing” was used which may be part of the confusion. $\endgroup$ – Dan Boschen Apr 9 at 11:24
  • $\begingroup$ @marcus I would slightly modify the statement "matched filtering only is an optimal technique if you want to maximize SNR is an AWGN channel". Even in wireless systems matched filtering is optimal in low SNR conditions, where the received signal is projected along the wireless channel..in the context of wireless systems, coherent detection has the definition of detection when the wireless channel is known at the receiver and thus matched filtering is possible and infact optimal at low SNR $\endgroup$ – Dsp guy sam Apr 9 at 18:01

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