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Decision feedback equalizer employing fixed ratio postcursor taps for minimizing noise and intersymbol interference in signals conveyed over high speed data service loop

  • US 5,414,733 A
  • Filed: 12/20/1993
  • Issued: 05/09/1995
  • Est. Priority Date: 12/20/1993
  • Status: Expired due to Term
First Claim
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1. A decision feedback equalizer comprising:

  • a linear transversal filter section to which successive received symbols of an input symbol sequence are sequentially introduced, said linear transversal filter section including a feedforward multistage delay line comprised of a series of 1st-Mth symbol value storage stages, M being an integer greater than 1, and a feedforward weighting and summing stage operative to multiply respective ones of a plurality of 1st-Mth weighting coefficients W1 -WM by respective ones of a plurality of 1st-Mth received symbols stored in said feedforward multistage delay line, and thereby obtain a plurality of 1st-Mth products, said 1st-Mth products being summed to provide a weighted and summed feedforward symbol value output;

    a symbol decision unit which is coupled to receive a differential symbol value associated with a difference between said weighted and summed feedforward symbol value output and a weighted and summed feedback symbol value output and being operative to generate a received symbol value estimate in accordance with said difference; and

    a decision feedback transversal filter section to which successive symbol value estimates generated by said symbol decision unit are sequentially applied, said decision feedback transversal filter section including a feedback multistage delay line comprised of a series of 1st through Nth symbol value storage stages, N being an integer greater than 1, and a feedback weighting and summing stage operative to multiply respective ones of a plurality of 1st through Nth weighting coefficients by respective ones of a plurality of 1st through Nth symbol decision outputs stored in said feedback multistage delay line, and thereby obtain a plurality of 1st through Nth products, said 1st through Nth products being summed to provide a weighted and summed feedback output, said weighted and summed feedback output being differentially combined with said weighted and summed feedforward symbol value output of said linear transversal filter section and the resulting differential signal being applied to said symbol decision unit which outputs received symbol value estimates; and

    whereinsaid feedforward weighting and summing stage of said linear transversal filter section has its largest valued, cursor weighting coefficient WC associated with an M-Kth symbol stage of said feedforward multistage delay line, where K is an integer equal to or greater than 1, and K respective postcursor weighting coefficients WM-K to WM associated with the last K symbol stages of said feedforward multistage delay line having fractional weighting coefficients of said cursor weighting coefficients WC.

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