Disk drive measuring down-track spacing of read sensors

• US 9,257,145 B1
• Filed: 04/29/2014
• Issued: 02/09/2016
• Est. Priority Date: 11/27/2013
• Status: Active Grant

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: Soderbloom, Paul E., Giovenzana, Davide, Sheperek, Michael W.
• Primary Examiner(s): HINDI, NABIL Z
• Application Number:
  US14/264,244
• Time in Patent Office: 651 Days
• Field of Search: 360/39, 360/77.13, 360/64, 360/69, 360/75, 360/77.08, 360/77.11, 360/70
• US Class Current: 1/1
• CPC Class Codes: G11B 20/10222 clock-related aspects, e.g. phase or frequency adjustment or bit synchronisation dedicated sync patterns in the modulation code G11B20/1403

Abstract

A disk drive is disclosed comprising a disk comprising a track, wherein the track comprises a sync mark. The disk drive further comprises a head comprising a plurality of read sensors including a first read sensor, and a second read sensor separated from the first read sensor by a down-track spacing. A first time-stamp (TS1) is generated after detecting the sync mark using the first read sensor as the disk rotates, and a second time-stamp (TS2) is generated after detecting the sync mark using the second read sensor as the disk rotates. A calibration value representing the down-track spacing is generated based on the TS1 and the TS2.

Claims

1. A disk drive comprising:

a disk comprising a track, wherein the track comprises a sync mark;

a head comprising a plurality of read sensors including a first read sensor, and a second read sensor separated from the first read sensor by a down-track spacing; and

control circuitry configured to;

generate a first time-stamp (TS1) after detecting the sync mark using the first read sensor as the disk rotates;

generate a second time-stamp (TS2) after detecting the sync mark using the second read sensor as the disk rotates; and

generate a calibration value representing the down-track spacing based on the TS1 and the TS2.

2. The disk drive as recited in claim 1, wherein the control circuitry is further configured to generate the calibration value based on a difference between the TS1 and the TS2.

3. The disk drive as recited in claim 1, wherein the control circuitry is further configured to:

sample a read signal generated by the first read sensor based on a reference clock to generate signal samples;

detect the sync mark based on the signal samples; and

generate the TS1 based on the reference clock.

4. The disk drive as recited in claim 3, wherein the control circuitry is further configured to:

detect a zero-phase start value based on the signal samples;

detect the sync mark based on the zero-phase start value;

clock a counter based on the reference clock;

generate an integer part of the TS1 based on the counter when the sync mark is detected; and

generate a fractional part of the TS1 based on the zero-phase start value.

5. The disk drive as recited in claim 1, wherein the control circuitry is further configured to measure the down-track offset at a plurality of different radial locations across the disk.

6. The disk drive as recited in claim 1, wherein the control circuitry is further configured to combine a first read signal generated by the first read sensor with a second read signal generated by the second read sensor based on the measured down-track spacing.

7. The disk drive as recited in claim 6, wherein the control circuitry is further configured to combine samples of the first read signal with samples of the second read signal based on the measured down-track spacing.

8. The disk drive as recited in claim 1, wherein the control circuitry is further configured to:

sample a first read signal generated by the first read sensor to generate first signal samples;

sample a second read signal generated by the second read sensor to generate second signal samples; and

execute a two-dimensional equalization of the first signal samples and the second signal samples.

9. The disk drive as recited in claim 8, wherein the control circuitry is further configured to execute the two-dimensional equalization in order to reduce inter-track interference (ITI) in one dimension.

10. A method of operating a disk drive, the method comprising:

generating a first time-stamp (TS1) after detecting a sync mark on a disk using a first read sensor as the disk rotates;

generating a second time-stamp (TS2) after detecting the sync mark using a second read sensor as the disk rotates; and

generating a calibration value representing a down-track spacing between the first read sensor and the second read sensor based on the TS1 and the TS2.

11. The method as recited in claim 10, further comprising generating the calibration value based on a difference between the TS1 and the TS2.

12. The method as recited in claim 10, further comprising:

sampling a read signal generated by the first read sensor based on a reference clock to generate signal samples;

detecting the sync mark based on the signal samples; and

generating the TS1 based on the reference clock.

13. The method as recited in claim 12, further comprising:

detecting a zero-phase start value based on the signal samples;

detecting the sync mark based on the zero-phase start value;

clocking a counter based on the reference clock;

generating an integer part of the TS1 based on the counter when the sync mark is detected; and

generating a fractional part of the TS1 based on the zero-phase start value.

14. The method as recited in claim 10, further comprising measuring the down-track offset at a plurality of different radial locations across the disk.

15. The method as recited in claim 10, further comprising combining a first read signal generated by the first read sensor with a second read signal generated by the second read sensor based on the measured down-track spacing.

16. The method as recited in claim 15, further comprising combining samples of the first read signal with samples of the second read signal based on the measured down-track spacing.

17. The method as recited in claim 10, further comprising:

sampling a first read signal generated by the first read sensor to generate first signal samples;

sampling a second read signal generated by the second read sensor to generate second signal samples; and

executing a two-dimensional equalization of the first signal samples and the second signal samples.

18. The method as recited in claim 17, further comprising executing the two-dimensional equalization in order to reduce inter-track interference (ITI) in one dimension.