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Method and apparatus for QPR carrier recovery

  • US 5,271,041 A
  • Filed: 03/16/1992
  • Issued: 12/14/1993
  • Est. Priority Date: 03/16/1992
  • Status: Expired due to Term
First Claim
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1. A carrier recovery circuit for generating the inphase and quadrature phases of a demodulation carrier coherent with the carrier of a quadrature partial response (QPR) signal of the form Mi * sin (ω

  • c t)+Mq (t) * cos (ω

    c t), where Mi (t) and Mq (t) are encoded partial response information modulations of the inphase and quadrature phases of a carrier of angular frequency [(ω

    c t)]ω

    c, said carrier recovery circuit comprising;

    means for generating analog signals representing the demodulated values of the information signal Mi (t) and its inverse *Mi (t);

    means for generating analog signals representing the demodulated values of the information signal Mq (t) and its inverse *Mq (t);

    means for generating an error signal based on a selected combination of a analog signals Mi (t), *Mi (t) and the analog signals Mq, *Mq ;

    means for generating a variable frequency carrier signal in response to a control signal;

    means for generating said control signal in response to said error signal which varies the frequency of said variable frequency carrier signal to minimize the error signal;

    means for splitting said variable frequency carrier signal into an inphase phase path and a quadrature phase path; and

    means located in said quadrature phase path for shifting the variable frequency carrier signal at least 90°

    inphase.

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