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Carrier recovery system using acquisition and tracking modes and automatic carrier-to-noise estimation

  • US 5,471,508 A
  • Filed: 08/20/1993
  • Issued: 11/28/1995
  • Est. Priority Date: 08/20/1993
  • Status: Expired due to Fees
First Claim
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1. In a communications receiver, apparatus for recovering a carrier signal from a received signal and for producing de-rotated symbols therefrom, said apparatus comprising:

  • means, responsive to an incoming stream of symbols obtained from said received signal and to a reference carrier signal, for producing a stream of de-rotated symbols;

    tracking slicing means for converting each one of said de-rotated symbols into a corresponding first sliced value so as to define a stream of first sliced values, wherein each of said first sliced values defines a corresponding symbol in a pre-selected constellation;

    acquisition slicing means for converting ones of said de-rotated symbols into corresponding second sliced values, wherein each one of said second sliced values is specified by a pre-defined attribute of a corresponding one of said de-rotated symbols;

    means, operative in response to a mode select signal, for comparing said each one of said de-rotated symbols to a corresponding one of selectively either said first or second sliced values in order to generate a phase error signal;

    means, operative in response to said stream of first sliced values and to said stream of de-rotated symbols, for producing a mode error signal;

    means, responsive to said mode error signal and a switching threshold value, for producing said mode select signal; and

    means, responsive to said phase error signal, for generating said reference carrier.

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