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Signal presence detector and method

  • US 4,363,138 A
  • Filed: 11/27/1978
  • Issued: 12/07/1982
  • Est. Priority Date: 11/27/1978
  • Status: Expired due to Term
First Claim
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1. A signal presence detector for an input signal having a known spectral distribution but accompanied by strong noise energy which may provide a negative signal-to-noise ratio, comprising:

  • a common input for receiving the input signal;

    a first bandpass filter coupled to the common input and responsive to the input signal, the first bandpass filter encompassing one selected region within the spectral distribution;

    a second bandpass filter coupled to the common input and responsive to the input signal, the second bandpass filter encompassing a second selected region within the spectral distribution;

    a detector;

    switching means for applying the outputs of said first and second bandpass filters to said detector in time shared fashion; and

    means coupled to said detector and responsive to received energy levels from said bandpass filters which differ by at least a predetermined minimum amount for indicating the presence of the input signal;

    the first and second bandpass filters having center frequencies lying at different regions within the spectral distribution, the signal having a spread spectrum characteristic and the center frequency of said first bandpass filter being at the center frequency of the spread spectrum.

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