Disk drive margining read channel using predictable disturbance samples generated as a function of a written pattern
View Patent ↗A disk drive is disclosed comprising a head actuated over a disk having a plurality of tracks. A pattern is read from the disk to generate a read signal, and the read signal is sampled to generate read samples. Predictable disturbing samples are generated as a function of the pattern. The predictable disturbing samples are added to the read samples to generate disturbed samples, and a data sequence is detected from the disturbed samples.
1. A disk drive comprising:
a disk comprising a plurality of tracks;
a head actuated over the disk; and
control circuitry operable to:
read a pattern from the disk to generate a read signal;
sample the read signal to generate read samples;
generate predictable disturbing samples as a function of the pattern;
add the predictable disturbing samples to the read samples to generate disturbed samples; and
detect a data sequence from the disturbed samples.
2. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:
generate expected samples as a function of the pattern, wherein the expected samples correspond to the read samples; and
generate the predictable disturbing samples as a function of the expected samples.
3. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to equalize the read samples according to a target response and add the predictable disturbing samples to the equalized read samples.
4. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to equalize the disturbed samples prior to detecting the data sequence.
5. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to write the pattern to the disk.
6. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to generate the predictable disturbing samples as a function of the detected data sequence.
7. The disk drive as recited in claim 2 , wherein the control circuitry is further operable to scale the expected samples to generate the predictable disturbing samples.
8. The disk drive as recited in claim 2 , wherein the control circuitry is further operable to square the expected samples to generate the predictable disturbing samples.
9. The disk drive as recited in claim 2 , wherein the control circuitry is further operable to index a lookup table using the expected samples to generate the predictable disturbing samples.
10. The disk drive as recited in claim 9 , wherein the lookup table simulates at least one of adjacent track interference, a defect on the disk, and a sampling timing error.
11. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to index a lookup table using the pattern to generate the predictable disturbing samples.
12. The disk drive as recited in claim 11 , wherein the lookup table simulates a baseline wander.
13. A method of operating a disk drive comprising a head actuated over a disk including a plurality of tracks, the method comprising:
reading a pattern from the disk to generate a read signal;
sampling the read signal to generate read samples;
generating predictable disturbing samples as a function of the pattern;
adding the predictable disturbing samples to the read samples to generate disturbed samples; and
detecting a data sequence from the disturbed samples.
14. The method as recited in claim 13 , further comprising:
generating expected samples as a function of the pattern, wherein the expected samples correspond to the read samples; and
generating the predictable disturbing samples as a function of the expected samples.
15. The method as recited in claim 13 , further comprising equalizing the read samples according to a target response and adding the predictable disturbing samples to the equalized read samples.
16. The method as recited in claim 13 , further comprising equalizing the disturbed samples prior to detecting the data sequence.
17. The method as recited in claim 13 , further comprising writing the pattern to the disk.
18. The method as recited in claim 13 , further comprising generating the predictable disturbing samples from the detected data sequence.
19. The method as recited in claim 14 , further comprising scaling the expected samples to generate the predictable disturbing samples.
20. The method as recited in claim 14 , further comprising squaring the expected samples to generate the predictable disturbing samples.
21. The method as recited in claim 14 , further comprising indexing a lookup table using the expected samples to generate the predictable disturbing samples.
22. The method as recited in claim 21 , wherein the lookup table simulates at least one of adjacent track interference, a defect on the disk, and a sampling timing error.
23. The method as recited in claim 13 , further comprising indexing a lookup table using the pattern to generate the predictable disturbing samples.
24. The method as recited in claim 23 , wherein the lookup table simulates a baseline wander.