Adaptive noise-predictive partial-response equalization for channels with spectral nulls

A method for detecting a digital information sequence x(D) transmitted via a channel exhibiting spectral nulls and/or near nulls, said apparatus comprising:

• shaping said channel to a desired partial-response transfer function using a partial-response linear equalizer (32;
• 72) having a transfer function d(D) such that the discrete time output sequence z(D), at an output of said partial-response linear equalizer (32;
• 72), has spectral nulls approximately where the channel response has spectral nulls and/or near nulls;
• estimating said transmitted digital information sequence x(D) and providing zero-delay tentative decisions x(D) at an output line (38;
• 78) using a partial response Viterbi detector (33;
• 73);
• isolating noise components of said discrete time output sequence z(D) using a partial-response filter (34;74) followed by a noise predictor (35;
• 75) being connected to said partial-response Viterbi detector (33;
• 73);
• isolating residual interference components of said discrete time output sequence z(D) using said partial-response filter (34;74) followed by said noise predictor (35;
• 75) being connected to said partial-response Viterbi detector (33;
• 73);
• predicting future noise components and residual interference components using said partial-response filter (34;
• 74) followed by said noise predictor (35;
• 75) being connected to said partial-response Viterbi detector (33;
• 73);
• and
• adapting said method by using a second partial-response filter (39;
• 79) and a predictor-coefficient estimator (50;
• 80) having coefficients associated therewith, said second partial-response filter operating on said zero-delay tentative decisions x(D) to provide a shaped output sequence {r.sub.k } which is subtracted from said discrete time output sequence z(D) to obtain an error sequence {e'.sub.k } used for updating coefficients {d.sub.i } of said partial-response linear equalizer (32;
• 72) .