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Abstract

A sampled amplitude read channel is disclosed for disk storage systems that employs an EPR4 remod/demod sequence detector. To reduce the complexity of timing recovery, gain control and adaptive equalization, the channel samples are initially equalized into a PR4 partial response so that a simple slicer circuit can generate estimated sample values. The PR4 equalized channel samples are then passed through a 1+D filter to generate EPR4 equalized channel samples which are processed by an EPR4 Viterbi sequence detector to generate a preliminary binary sequence. The preliminary binary sequence is remodulated into an estimated or ideal PR4 sample sequence which is subtracted from the PR4 equalized channel samples to generate an error sample sequence. An error pattern detector processes the error sample sequence to detect the dominant error events associated with the EPR4 Viterbi sequence detector.

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