SYSTEMS AND METHODS FOR CALIBRATING READ AND WRITE OPERATIONS IN TWO DIMENSIONAL MAGNETIC RECORDING

• US 20150022916A1
• Filed: 07/15/2014
• Published: 01/22/2015
• Est. Priority Date: 07/16/2013
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell World Trade Limited (Marvell Technology Group Limited)
• Inventors: Zou, Qiyue, Madden, Michael, Burd, Gregory
• Granted Patent: US 9,311,937 B2
• Time in Patent Office: Days
• US Class Current: 360/31
• CPC Class Codes: G11B 20/10 Digital recording or reproducing
• CPC Class Codes: G11B 5/012 Recording on, or reproducing or erasing from, magnetic disks G11B17/00, G11B19/00 take precedence
• CPC Class Codes: G11B 5/455 Arrangements for functional testing of heads; Measuring arrangements for heads
• CPC Class Codes: G11B 5/4886 relative to rotating disc
• CPC Class Codes: G11B 5/58 with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following spacing means incorporated in the head structure G11B5/187, G11B5/255, G11B5/3106
• CPC Class Codes: G11B 5/59627 Aligning for runout, eccentricity or offset compensation G11B5/5534, G11B5/59677, G11B5/59688 take precedence
• CPC Class Codes: G11B 5/59683 for magnetoresistive heads

Abstract

Systems and methods are provided for calibrating signals retrieved from a storage device using a first reader and a second reader. The systems and methods further include reading a first signal using the first reader and a second signal using the second reader. Control circuitry computes a calibration metric associated with the first reader and the second reader based on the combination of the first signal and the second signal. At least one of the first signal and the second signal is subsequently decoded based in part on the computed calibration metric.

Claims

1. A method for calibrating signals retrieved from a storage device using a first reader and a second reader, the method comprising:

reading, using control circuitry, a first signal using the first reader and a second signal using the second reader;

computing, using the control circuitry, a calibration metric based on a combination of the first signal and the second signal; and

decoding at least one of the first signal and the second signal based in part on the computed calibration metric.

2. The method of claim 1, wherein:

the first signal is associated with a first track of the storage device; and

the second signal is associated with a second track of the storage device.

3. The method of claim 1, wherein the calibration metric comprises a time offset between the first signal and the second signal.

4. The method of claim 1, wherein computing the calibration metric comprises:

determining a first time period ranging from the first reader detecting a servo address mark to the first reader detecting a data address mark;

determining a second time period ranging from the second reader detecting the servo address mark to the second reader detecting the data address mark; and

computing a time offset based on the first time period and the second time period.

5. The method of claim 1, wherein computing the calibration metric comprises:

correlating a first portion of the first signal and a second portion of the second signal to obtain a cross-correlation sequence;

detecting a peak in the cross-correlation sequence; and

computing a time offset based on the detected peak of the cross-correlation sequence.

6. The method of claim 5, wherein the first portion and the second portion correspond to one of a pseudo-random bit sequence and a sector sync marker.

7. The method of claim 1, wherein computing the calibration metric comprises:

computing a phase relation between a first portion of the first signal and a second portion of the second signal to obtain a phase shift between the first reader and the second reader; and

determining a time offset based on the phase shift.

8. The method of claim 1, wherein the calibration metric comprises a cross-track distance between the first reader and the second reader, and computing the calibration metric comprises:

estimating a position offset of the first reader relative to the second reader based on a reference signal; and

computing an average of the position offset of the first reader relative to the second reader to obtain the calibration metric.

9. The method of claim 8, wherein the averaged position offset is used to improve an accuracy of a position estimation signal (PES).

10. The method of claim 1, further comprising:

writing, using the control circuitry, a third signal to the storage device based on the calibration metric.

11. The method of claim 1, wherein the decoding comprises performing joint decoding of the first signal and the second signal based on the calibration metric.

12. The method of claim 1, wherein the calibration metric is a first calibration metric, the method further comprising:

computing a second calibration metric associated with a writer and at least one of the first reader and the second reader; and

recording data on the storage device using the writer based on the second calibration metric.

13. A system for calibrating signals retrieved from a storage device, the system comprising:

a first reader configured to read a first signal;

a second reader configured to read a second signal;

control circuitry configured to compute a calibration metric based on a combination of the first signal and the second signal; and

a decoder configured to decode at least one of the first signal and the second signal based in part on the computed calibration metric.

14. The system of claim 13, wherein:

the first signal is associated with a first track of the storage device; and

the second signal is associated with a second track of the storage device.

15. The system of claim 13, wherein the calibration metric comprises a time offset between the first signal and the second signal.

16. The system of claim 13, wherein the control circuitry is further configured to:

determine a first time period ranging from the first reader detecting a servo address mark to the first reader detecting a data address mark;

determine a second time period ranging from the second reader detecting the servo address mark to the second reader detecting the data address mark; and

compute a time offset based on the first time period and the second time period.

17. The system of claim 13, wherein the control circuitry is further configured to:

correlate a first portion of the first signal and a second portion of the second signal to obtain a cross-correlation sequence;

detect a peak in the cross-correlation sequence; and

compute a time offset based on the detected peak of the cross-correlation sequence.

18. The system of claim 13, wherein the first portion and the second portion correspond to one of a pseudo-random bit sequence and a sector sync marker.

19. The system of claim 13, wherein the control circuitry is further configured to:

compute a phase relation between a first portion of the first signal and a second portion of the second signal to obtain a phase shift between the first reader and the second reader; and

determine a time offset based on the phase shift.

20. The system of claim 13, wherein the calibration metric comprises a cross-track distance between the first reader and the second reader, and the control circuitry is further configured to:

estimate a position offset of the first reader relative to the second reader based on a reference signal; and

compute an average of the position offset of the first reader relative to the second reader to obtain the calibration metric.

21. The system of claim 20, wherein the control circuitry is further configured to improve an accuracy of a position estimation signal (PES) using the averaged position offset.

22. The system of claim 13, wherein the control circuitry is further configured to:

write a third signal to the storage device based on the calibration metric.

23. The system of claim 13, wherein the control circuitry is configured to perform the decoding by performing joint decoding of the first signal and the second signal based on the calibration metric.

24. The system of claim 13, wherein the calibration metric is a first calibration metric, and the control circuitry is further configured to:

compute a second calibration metric associated with a writer and at least one of the first reader and the second reader; and

record data on the storage device using the writer based on the second calibration metric.