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Abstract

A sampled amplitude read channel is disclosed for disk storage systems (e.g., magnetic or optical) comprising a sampling device for sampling the analog read signal emanating from the read head positioned over a disk storage medium, a channel equalizer for equalizing the signal samples according to a desired partial response, a trellis sequence detector for detecting a preliminary sequence from the equalized signal samples, and a post processor for correcting errors in the preliminary sequence, including errors caused by the channel equalizers correlating the noise in the read signal. The preliminary sequence detected by the sequence detector is remodulated into ideal partial response samples and then subtracted from the actual signal samples to generate a sequence of sample errors. The sample errors are then filtered by a sample error filter, and the filtered sample errors are correlated with error event sequences corresponding to the most likely error events of the trellis sequence detector. The sample error filter compensates for the noise correlating effect of the channel equalizers by effectively whitening the noise to provide a closer approximation to an optimum maximum likelihood detector. When an error event is detected, the preliminary sequence is corrected with a correction sequence corresponding to the detected error event.

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