Disk drive cross correlating track crossing signal with ideal signal to calibrate jog value
View Patent ↗A disk drive is disclosed comprising a disk including a plurality of tracks, and a head actuated over the disk, wherein the head comprises a read element radial offset from a write element. A jog value corresponding to the radial offset is calibrated by writing data to a plurality of tracks, reading the plurality of written tracks to generate an actual track crossing signal, cross correlating the actual track crossing signal with an ideal track crossing signal to generate a cross correlation signal, and calibrating the jog value in response to the cross correlation signal.
1. A disk drive comprising:
a disk comprising a plurality of tracks;
a head actuated over the disk, wherein the head comprises a read element radial offset from a write element; and
control circuitry operable to calibrate a jog value corresponding to the radial offset by:
writing data to a plurality of tracks;
reading the plurality of written tracks to generate an actual track crossing signal;
cross correlating the actual track crossing signal with an ideal track crossing signal to generate a cross correlation signal; and
calibrating the jog value in response to the cross correlation signal.
2. The disk drive as recited in claim 1 , wherein the control circuitry is operable to generate a data point in the cross correlation signal by introducing a phase offset between the actual track crossing signal and the ideal track crossing signal.
3. The disk drive as recited in claim 2 , wherein the control circuitry is operable to generate multiple data points in the cross correlation signal by introducing multiple phase offsets between the actual track crossing signal and the ideal track crossing signal.
4. The disk drive as recited in claim 3 , wherein the control circuitry is operable to calibrate the jog value relative to a maximum of the cross correlation signal.
5. The disk drive as recited in claim 3 , wherein the control circuitry is operable to calibrate the jog value relative to a minimum of the cross correlation signal.
6. The disk drive as recited in claim 1 , wherein the control circuitry is operable to:
generate samples of a first track crossing signal at a first resolution when reading the written tracks; and
interpolate the samples to generate the actual track crossing signal at a second resolution higher than the first resolution.
7. The disk drive as recited in claim 6 , wherein the control circuitry is operable to generate the cross correlation signal at the second resolution.
8. The disk drive as recited in claim 1 , wherein the control circuitry is operable to calibrate a plurality of jog values each corresponding to a different radial location of the disk.
9. A method of operating a disk drive comprising a head actuated over a disk including a plurality of tracks, wherein the head comprises a read element radial offset from a write element, the method comprising calibrating a jog value corresponding to the radial offset by:
writing data to a plurality of tracks;
reading the plurality of written tracks to generate an actual track crossing signal;
cross correlating the actual track crossing signal with an ideal track crossing signal to generate a cross correlation signal; and
calibrating the jog value in response to the cross correlation signal.
10. The method as recited in claim 9 , further comprising generating a data point in the cross correlation signal by introducing a phase offset between the actual track crossing signal and the ideal track crossing signal.
11. The method as recited in claim 10 , further comprising generating multiple data points in the cross correlation signal by introducing multiple phase offsets between the actual track crossing signal and the ideal track crossing signal.
12. The method as recited in claim 11 , further comprising calibrating the jog value relative to a maximum of the cross correlation signal.
13. The method as recited in claim 11 , further comprising calibrating the jog value relative to a minimum of the cross correlation signal.
14. The method as recited in claim 9 , further comprising:
generating samples of a first track crossing signal at a first resolution when reading the written tracks; and
interpolating the samples to generate the actual track crossing signal at a second resolution higher than the first resolution.
15. The method as recited in claim 14 , further comprising generating the cross correlation signal at the second resolution.
16. The method as recited in claim 9 , further comprising calibrating a plurality of jog values each corresponding to a different radial location of the disk.