Disk drive comprising a trellis detector having a read signal whitener in the ACS circuit
AssigneeWestern Digital Technologies, Inc.
InventorAlvin J. Wang
Life of this patent
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Abstract
A disk drive is disclosed comprising a disk, a head actuated over the disk to generate a read signal, and a trellis detector for detecting an estimated data sequence from the read signal. The trellis detector comprises a sampling device operable to sample the read signal to generate a sequence of signal sample values, and a plurality of add/compare/select (ACS) circuits each corresponding to a state in a trellis. Each ACS circuit comprises a first and second branch metric calculators for computing first and second branch metrics in response to first and second errors adjusted in response to first and second deltas that compensate for a distortion in the read signal.
Claims20
A disk drive comprising:
- a disk;
- a head actuated over the disk to generate a read signal;
- a sampling device operable to sample the read signal to generate a sequence of signal sample values;
- and
- a trellis detector for detecting an estimated data sequence from the signal sample values, the trellis detector comprising a plurality of add/compare/select (ACS) circuits each corresponding to a state in a trellis, wherein each ACS circuit comprises:
- a first error generator for generating a first error relative to a signal sample value and a first expected value corresponding to a first branch in the trellis;
- a first adder for adjusting the first error in response to a first delta to generate a first adjusted error;
- a first branch metric calculator for computing a first branch metric in response to the first adjusted error;
- a first update circuit for updating the first delta in response to the first adjusted error;
- a second error generator for generating a second error relative to the signal sample value and a second expected value corresponding to a second branch in the trellis;
- a second adder for adjusting the second error in response to a second delta to generate a second adjusted error;
- a second branch metric calculator for computing a second branch metric in response to the second adjusted error;
- and
- a second update circuit for updating the second delta in response to the second adjusted error.
A method of operating a disk drive, the disk drive comprising a disk, a head actuated over the disk to generate a read signal, and a trellis detector for detecting an estimated data sequence from the read signal, the method comprising:
- sampling the read signal to generate a sequence of signal sample values;
- generating a first error relative to a signal sample value and a first expected value corresponding to a first branch in the trellis;
- adjusting the first error in response to a first delta to generate a first adjusted error;
- computing a first branch metric in response to the first adjusted error;
- updating the first delta in response to the first adjusted error;
- generating a second error relative to the signal sample value and a second expected value corresponding to a second branch in the trellis;
- adjusting the second error in response to a second delta to generate a second adjusted error;
- computing a second branch metric in response to the second adjusted error;
- and
- updating the second delta in response to the second adjusted error.
Dependencies are inferred from the claim text.