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Doppler frequency analysis of radar signals

  • US 4,400,700 A
  • Filed: 06/08/1981
  • Issued: 08/23/1983
  • Est. Priority Date: 06/08/1981
  • Status: Expired due to Fees
First Claim
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1. A radar system which responds to distinctive Doppler step modulation resulting from the movement of human targets, comprising:

  • a Doppler radar having a first intermediate frequency signal output modulated by a Doppler signal within a first low frequency range, a frequency modulation (FM) detector coupled to said radar to receive said first intermediate frequency and Doppler signal, said FM detector adapted to respond only to step frequency modulation on said first intermediate frequency, said step frequency being within a second range of low frequencies lower than said first frequency range and representing the frequency of movement of human targets, a plurality of parallel tuned filters operative within said second range of frequencies and connected to the output of said FM detector to split the detected step modulation frequencies into a number or contiguous frequency bands representing targets stepping at different rates, and a plurality of indicators respectively connected to the outputs of said filters to indicate the presence of moving targets at different step frequencies.

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