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Decision-directed, automatic frequency control technique for non-coherently demodulated M-ARY frequency shift keying

  • US 4,518,922 A
  • Filed: 01/17/1983
  • Issued: 05/21/1985
  • Est. Priority Date: 01/17/1983
  • Status: Expired due to Fees
First Claim
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1. For use in a demodulator for detecting information symbols which are encoded in the form of a frequency shift keying carrier signal, said demodulator containing means for generating a local carrier signal, an arrangement for controlling said local carrier signal for tracking frequency changes therein comprising:

  • first means for combining said local carrier signal and an incoming frequency shift keying signal to be demodulated and producing therefrom signals representative of the modulation information contained in said incoming signals;

    second means, coupled to said first means, for deriving output signals representative of the information symbols by which said carrier signal was modulated to form said frequency shift keying signals;

    third means, responsive to signals produced by said first and second means, for deriving error signals representative of the frequency error in said local carrier signal; and

    linear discriminator means, responsive to said error signals, for controlling said local carrier signal generating means so as to track frequency changes in said incoming frequency shift keying signal to be demodulated.

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