Decision feedback equalization implementation of partial-respons

Dynamic magnetic information storage or retrieval – General recording or reproducing – Specifics of equalizing

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360 51, 371 211, 371 436, 375233, G11B 535

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058221433

ABSTRACT:
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.

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