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Timing and automatic frequency control of digital receiver using the cyclic properties of a non-linear operation

  • US 5,282,228 A
  • Filed: 12/09/1991
  • Issued: 01/25/1994
  • Est. Priority Date: 12/09/1991
  • Status: Expired due to Term
First Claim
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1. A method for correcting the symbol sampling time and carrier frequency error in a received modulated digital signal, comprising the steps of:

  • demodulating the modulated digital signal, by mixing it with a local reference oscillator to provide a baseband signal;

    sampling the baseband signal to provide discrete-time, in-phase (I) and quadrature (Q) components thereof;

    performing a first non-linear operation on the I and Q components, to produce a first composite signal having a first phase component related to a symbol timing error and a second phase component related to a carrier frequency error;

    performing a second non-linear operation on the I and Q components, to produce a second composite signal having a first phase component related to the symbol timing error and a second phase component related to the negative of the carrier frequency error;

    detecting the symbol timing error by comparing the first and second composite signals;

    detecting the carrier frequency error by comparing the first and second composite signals;

    adjusting the time of subsequent sampling steps according to the detected symbol timing error; and

    adjusting the frequency of the I and Q components according to the detected carrier frequency error.

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