Disk drive employing a sync mark detector comprising a matched filter and a dual polarity correlator
AssigneeWestern Digital Technologies, Inc.
InventorsGrant S. Christiansen, Mark D. Hagen
Life of this patent
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Abstract
The present invention may be regarded as a disk drive comprising a disk having a plurality of data tracks, each data track comprising a plurality of sectors. A sync mark detector detects a sync mark pattern in a sector by filtering a read signal with a matched filter having an impulse response substantially matched to a dibit response of the disk drive. The output of the matched filter is correlated with a dual polarity correlator to generate first and second correlated signals. The sync mark pattern is detected when either the first or second correlated signals exceeds a threshold.
Claims4
A disk drive comprising:
- (a) a disk comprising a plurality of data tracks, each data track comprising a plurality of sectors, each sector comprising:
- a preamble field for storing a predetermined periodic data sequence;
- a sync field for storing a predetermined sync mark pattern;
- and
- a data field for storing data;
- (b) a head actuated radially over the disk for generating a read signal;
- (c) a sync mark detector for detecting the sync mark pattern in the read signal, wherein the sync mark pattern is recorded on the disk in a binary sequence, a “1” bit in the binary sequence is represented by a dibit recorded on the disk, the dibit generating a dibit response in the read signal, and a “0” bit in the binary sequence is represented by the absence of a dibit recorded on the disk, the sync mark detector comprising:
- a matched filter having an impulse response substantially matched to the dibit response, the matched filter for filtering the read signal to generate a filtered signal;
- a first threshold comparator for comparing the filtered signal to a positive threshold and to a negative threshold, wherein:
- the first threshold detector outputs a first estimated sequence corresponding to the positive threshold;
- the first threshold detector outputs a second estimated sequence corresponding to the negative threshold;
- a “1” bit is detected in the first estimated sequence when the filtered signal exceeds the positive threshold and a “0” bit is detected in the first estimated sequence when the filtered signal does not exceed the positive threshold;
- and
- a “1” bit is detected in the second estimated sequence when the filtered signal exceeds the negative threshold and a “0” bit is detected in the second estimated sequence when the filtered signal does not exceed the negative threshold;
- a first correlator for correlating the first estimated sequence with the predetermined sync mark pattern to generate a first correlated signal;
- a second correlator for correlating the second estimated sequence with the predetermined sync mark pattern to generate a second correlated signal;
- and
- a second threshold comparator for comparing the first and second correlated signals to a threshold, wherein the sync mark pattern in the read signal is detected when either the first or second correlated signals exceeds the threshold.
A method of detecting a sync mark pattern in a disk drive, the disk drive comprising a disk comprising a plurality of data tracks, each data track comprising a plurality of sectors, each sector comprising a preamble field for storing a predetermined periodic data sequence, a sync field for storing the sync mark pattern, and a data field for storing the data, wherein the sync mark pattern is recorded on the disk in a binary sequence, a “1” bit in the binary sequence is represented by a dibit recorded on the disk, the dibit generating a dibit response in the read signal, and a “0” bit in the binary sequence is represented by the absence of a dibit recorded on the disk, the method comprising the steps of:
- (a) actuating a head radially over the disk to generate a read signal;
- (b) filtering the read signal with a matched filter having an impulse response substantially matched to the dibit response to generate a filtered signal;
- (c) comparing the filtered signal to a positive threshold and to a negative threshold to generate a first estimated sequence corresponding to the positive threshold and a second estimated sequence corresponding to the negative threshold, wherein:
- a “1” bit is detected in the first estimated sequence when the filtered signal exceeds the positive threshold and a “0” bit is detected in the first estimated sequence when the filtered signal does not exceed the positive threshold;
- and
- a “1” bit is detected in the second estimated sequence when the filtered signal exceeds the negative threshold and a “0” bit is detected in the second estimated sequence when the filtered signal does not exceed the negative threshold;
- (d) correlating the first estimated sequence with the sync mark pattern to generate a first correlated signal;
- (e) correlating the second estimated sequence with the sync mark pattern to generate a second correlated signal;
- and
- (f) comparing the first and second correlated signals to a threshold, wherein the sync mark pattern is detected in the read signal when either the first or second correlated signals exceeds the threshold.
Dependencies are inferred from the claim text.