Decision feedback equalization implementation of partial-response signaling in a magnetic recording channel

摘要

A partial-response maximum-likelihood (PRML) sequence detector with decision feedback equalization (DFE) for a disk drive read channel. The symbol recovery method for a disk drive read channel produces a sequence of samples X.sub.n of a magnetic readback signal with amplitudes representing the readback signal during corresponding sample intervals n=1-N. A DFE circuit generates a sequence of equalized samples y.sub.n and includes a feed-forward filter that removes precursor ISI from the sequence of sample signals x.sub.n to produce a sequence of feed-forward equalized samples w.sub.n, detection logic that translates the sequence of equalized samples y.sub.n into a sequence of detected symbols y.sub.n, and a feedback filter that filters the sequence of detected symbols y.sub. n to produce a sequence of equalization feedback values e.sub.n to offset postcursor ISI remaining in the sequence of feed-forward equalized samples w.sub.n. A combinational circuit receives the feed-forward equalized samples w.sub.n and the feedback values e.sub. n and combines a sample w.sub.k with an equalization feedback value e. sub.k to produce an equalized sample y.sub.k for each sample interval k in the range of k=1-N. A PRML sequence detector, such as a Viterbi detector, is used with the DFE circuit to recover a user data symbol a. sub.k for sample interval k corresponding to the equalized sample y.sub. k in response to the sequence of equalized samples y.sub.n. The detected symbols y.sub.n used in the feedback path are generated using separate detectors, which allows for feedback with a delay of only one sample interval.