Disk drive demodulating a time-based servo pattern
View Patent ↗A disk drive is disclosed including a disk having a first and second set of time-based servo patterns. The first set of time-based servo patterns comprises a first cyclical pattern that repeats radially over the disk, and the second set of time-based servo patterns comprises a second cyclical pattern that repeats radially over the disk, wherein each cyclical pattern comprises a plurality of timing marks. One of the first cyclical patterns overlaps at least part of a first servo track, and one of the second cyclical patterns overlaps at least part of the first servo track. At least one of the first and second set of time-based servo patterns are demodulated by detecting first and second time intervals relative to the timing marks, and a control signal for actuating the head is generated in response to the first and second time intervals.
1. A disk drive comprising:
(a) a disk comprising a first set of time-based servo patterns and a second set of time-based servo patterns that define a plurality of servo tracks, wherein:
the first set of time-based servo patterns comprises a first cyclical pattern that repeats radially over the disk;
the second set of time-based servo patterns comprises a second cyclical pattern that repeats radially over the disk;
each cyclical pattern comprises a plurality of timing marks; and
one of the first cyclical patterns overlaps at least part of a first servo track, and one of the second cyclical patterns overlaps at least part of the first servo track;
(b) a head actuated over the disk; and
(c) control circuitry operable to demodulate at least one of the first and second set of time-based servo patterns to generate a control signal used to position the head over the disk by:
detecting a first time interval relative to the timing marks;
detecting a second time interval relative to the timing marks; and
generating the control signal in response to the first and second time intervals;
wherein the first cyclical pattern overlaps the entire first servo track, and the second cyclical pattern overlaps a portion of the first servo track.
2. The disk drive as recited in claim 1 , wherein the first cyclical pattern is the same as the second cyclical pattern.
3. The disk drive as recited in claim 1 , wherein the first cyclical pattern is different from the second cyclical pattern.
4. The disk drive as recited in claim 1 , wherein the control circuitry processes the first set of time-based servo patterns to generate the control signal used to maintain the head over the first servo track.
5. The disk drive as recited in claim 4 , wherein the control circuitry processes the second set of time-based servo patterns to generate the control signal used to maintain the head over a second servo track adjacent the first servo track.
6. The disk drive as recited in claim 1 , wherein:
the first set of time-based servo patterns comprises a first timing mark;
the second set of time-based servo patterns comprises a second timing mark;
the first timing mark comprises a first timing mark pattern; and
the second timing mark comprises a second timing mark pattern different than the first timing mark pattern.
7. The disk drive as recited in claim 1 , wherein the first and second set of time-based servo patterns overlap in the circumferential direction such that the first and second set of time-based servo patterns share at least one timing mark.
8. The disk drive as recited in claim 1 , wherein:
at least one of the first and second set of time-based servo patterns comprises first and second timing marks;
the first timing mark comprises a first timing mark pattern; and
the second timing mark comprises a second timing mark pattern different than the first timing mark pattern.
9. The disk drive as recited in claim 8 , wherein the first and second set of time-based servo patterns overlap in the circumferential direction such that the first and second set of time-based servo patterns share at least one of the first timing marks.
10. A method of operating a disk drive, the disk drive comprising a disk having a first set of time-based servo patterns and a second set of time-based servo patterns that define a plurality of servo tracks, wherein:
the first set of time-based servo patterns comprises a first cyclical pattern that repeats radially over the disk;
the second set of time-based servo patterns comprises a second cyclical pattern that repeats radially over the disk;
each cyclical pattern comprises a plurality of timing marks; and
one of the first cyclical patterns overlaps at least part of a first servo track, and one of the second cyclical patterns overlaps at least part of the first servo track;
the disk drive further comprising a head actuated over the disk, the method comprising:
detecting a first time interval relative to the timing marks;
detecting a second time interval relative to the timing marks; and
generating a control signal in response to the first and second time intervals, the control signal for positioning the head over the disk;
wherein the first cyclical pattern overlaps the entire first servo track, and the second cyclical pattern overlaps a portion of the first servo track.
11. The method as recited in claim 10 , wherein the first cyclical pattern is the same as the second cyclical pattern.
12. The method as recited in claim 10 , wherein the first cyclical pattern is different from the second cyclical pattern.
13. The method as recited in claim 10 , wherein the first set of time-based servo patterns are processed to generate the control signal used to maintain the head over the first servo track.
14. The method as recited in claim 13 , wherein the second set of time-based servo patterns are processed to generate the control signal used to maintain the head over a second servo track adjacent the first servo track.
15. The method as recited in claim 10 , wherein:
the first set of time-based servo patterns comprises a first timing mark;
the second set of time-based servo patterns comprises a second timing mark;
the first timing mark comprises a first timing mark pattern; and
the second timing mark comprises a second timing mark pattern different than the first timing mark pattern.
16. The method as recited in claim 10 , wherein the first and second set of time-based servo patterns overlap in the circumferential direction such that the first and second set of time-based servo patterns share at least one timing mark.
17. The method as recited in claim 10 , wherein:
at least one of the first and second set of time-based servo patterns comprises first and second timing marks;
the first timing mark comprises a first timing mark pattern; and
the second timing mark comprises a second timing mark pattern different than the first timing mark pattern.
18. The method as recited in claim 17 , wherein the first and second set of time-based servo patterns overlap in the circumferential direction such that the first and second set of time-based servo patterns share at least one of the first timing marks.