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

Claim 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 sequence of M symbol value storage stages, and a feedforward weighting and summing stage operative to multiply symbols stored in respective storage stages of said feedforward multistage delay by respective ones of a plurality of M weighting coefficients, where M is an integer greater than one, and thereby obtain a plurality of M products, said M products being summed together to provide a weighted and summed feedforward symbol value output; a symbol decision unit coupled to receive a differential symbol value associated with the difference between said weighted and summed feedforward symbol value output of said linear transversal filter section and a weighted and summed feedback symbol value output, and outputting 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 N symbol value storage stages, where N is an integer greater than one, and a feedback weighting and summing stage operative to multiply respective ones of N weighting coefficients by respective ones of N symbol decision outputs stored in said feedback multistage delay line, and thereby obtain a plurality of N products, said N products being summed to provide said weighted and summed feedback symbol value output, said weighted and summed feedback symbol value 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 wherein said feedforward weighting and summing stage of said linear transversal filter section has a largest valued, cursor weighting coefficient W c 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 W M-K+1 to W M associated with the last K symbol stages of said feedforward multistage delay line.