Western Digital Technologies, Inc.

Manmohan K Sharma

Patrick J Lee

Alvin Jianjiang Wang

A disk drive is disclosed comprising a head actuated over a disk, wherein data is read from the disk to generate a read signal. The read signal is sampled to generate signal samples, and the signal samples are filtered with an equalizer filter to generate equalized samples. The equalized samples are filtered with a general noise whitening filter to generate general noise whitened samples. The general noise-whitened samples are filtered with a bank of data dependent noise whitening filters to generate data dependent noise whitened samples, and a data sequence is detected from the data dependent noise whitened samples.

Disk drive employing general noise whitening filter to reduce length of data dependent noise whitening filters

A disk drive is disclosed comprising a head actuated over a disk comprising a sector including a periodic pattern and sector data. The sector is read with the head to generate a read signal which is sampled at a sampling frequency with a signal sampler to generate signal samples. The signal samples representing the periodic pattern are processed to measure a frequency induced phase error based on k&#x3b4; where k represents a signal sample index and &#x3b4; is a fraction of 2&#x3c0;. The signal samples representing the sector data are processed to generate a data phase error. The data phase error is adjusted in response to the frequency induced phase error to generate an adjusted data phase error, and the signal sampler is controlled in response to the adjusted data phase error.

Disk drive adjusting digital phase locked loop over sector data with frequency induced phase error measured over preamble

A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of data tracks. A read signal emanating from the head is sampled to generate read samples, and first log-likelihood ratios (LLRs) are generated in response to the read samples. The first LLRs are biased to generate biased LLRs, and the biased LLRs are decoded into a data sequence, wherein the biased LLRs increase an error rate of the data sequence.

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Cupertino, CA, United States of America

Manmohan K Sharma