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Spectrum surveillance receiver system

  • US 4,501,020 A
  • Filed: 09/21/1982
  • Issued: 02/19/1985
  • Est. Priority Date: 09/15/1982
  • Status: Expired due to Fees
First Claim
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1. A spectrum surveillance apparatus for surveilling signals within a predetermined RF band and identifying the type of modulation of signals within said band, said apparatus comprising:

  • a receiver adapted to receive RF signals at an adjustable reception frequency within said RF band and convert said RF signals to IF signals having a predetermined IF;

    RF filter means for filtering signals input to said receiver, said filter means including a plurality of filters having bandwidths together spanning said RF band;

    first switch means for selectively passing said signals through the one of said filters having the bandwidth containing said reception frequency;

    IF filter means for filtering the output of said receiver, said filter means having at least one filter having a relatively broad passband and at least one filter having a relatively narrow passband, said broadband filter being normally connected to the output of said receiver and second switch means for switching the output of said receiver from said broadband filter to said narrowband filter;

    means for sampling the envelope of said IF signal;

    means responsive to said sampling means for providing signals representative of at least the mean, the variance, and the percentage of the samples of said signal which have at least one predetermined amplitude;

    a first comparator for comparing each said representative signal with a threshold value and providing a logical set of outputs corresponding to said representative signals;

    a second comparator for comparing said set of logical outputs with a plurality of sets of logical reference values, each distinctive of a particular modulation type, and providing a first output indicative of the type of modulation of said signal when said logical set of outputs substantially matches one of said sets of logical reference values or a second output when said set of logical outputs does not match any of said sets of reference values;

    means responsive to said second comparator second output for causing said second switch means to switch the output of said receiver from said broadband filter to said narrowband filter; and

    means for automatically indexing the frequency of reception of said receiver through at least a predetermined, variable band within said RF band at predetermined, variable frequency increments.

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