Granted Patent B1

US 9,424,878 · App. 14/614,403 · Granted Aug 23, 2016

Abstract

Claims (34)

1. A storage system comprising:

a magnetic storage medium;

a magnetic sensor comprising an array of read heads configured to read a data track on the magnetic storage medium; and

a head separation calculation circuit configured to calculate a phase offset between signals from a first and a second of the read heads in the array of read heads based on phase estimates for the signals, wherein the head separation calculation circuit is configured to correct for phase wrapping differences between the signals.

2. The storage system of claim 1 , wherein the head separation calculation circuit is configured to calculate a difference between phase measurements for the signals.

3. The storage system of claim 1 , wherein the head separation calculation circuit comprises a phase offset limiter operable to shift the phase offset to lie within a predetermined range.

4. The storage system of claim 1 , wherein the head separation calculation circuit comprises at least one phase wrapping calculator configured to apply a phase wrap to a version of the phase offset.

5. The storage system of claim 1 , wherein the head separation calculation circuit comprises a subtraction circuit configured to calculate differences between a version of the phase offset and phase-wrapped versions of the phase offset.

6. The storage system of claim 1 , wherein the head separation calculation circuit further comprises a comparator circuit configured to compare the differences with a threshold.

7. The storage system of claim 1 , wherein the head separation calculation circuit is configured to calculate an average phase offset, and to include the phase offset in the average phase offset only after accounting for phase wrapping in the phase offset.

8. The storage system of claim 1 , wherein the head separation calculation circuit is configured to calculate an average phase offset, and to include the phase offset in the average phase offset only when the phase offset is consistent with a phase offset reference value based on at least one previous phase offset.

9. The storage system of claim 1 , wherein the head separation calculation circuit comprises an accumulator configured to accumulate the phase offset, and a phase offset reference calculator circuit configured to update a phase offset reference value based on a value in the accumulator and on a number of phase offsets accumulated in the accumulator.

10. The storage system of claim 9 , wherein the phase offset reference calculator circuit is configured to update the phase offset reference value only when a number of phase offsets accumulated in the accumulator is equal to two to a power of an integer.

11. A method for calculating an average phase offset in a two dimensional magnetic recording system, comprising:

calculating a phase offset as a difference between a phase of a first signal derived from a first read head and a second phase of a second signal derived from a second read head;

correcting for phase wrapping differences between the phase offset and a previous phase offset;

determining whether the phase offset is consistent with the previous phase offset; and

calculating an average phase offset which includes the phase offset only if it is consistent with the previous phase offset.

12. The method of claim 11 , wherein correcting for phase wrapping difference comprises limiting the phase offset to a predetermined phase range.

13. The method of claim 12 , wherein the predetermined phase range is based at least in part on a preamble pattern read by the first read head and the second read head.

14. The method of claim 11 , wherein correcting for phase wrapping differences comprises generating phase wrapped versions of the phase offset.

15. The method of claim 14 , wherein the phase wrapped versions comprise a phase advanced version of the phase offset and a phase delayed version of the phase offset.

16. The method of claim 14 , wherein generating the phase wrapped versions comprises shifting the phase offset by a period of a preamble pattern used to calculate the phase offset.

17. The method of claim 11 , wherein determining whether the phase offset is consistent with the previous phase offset comprises determining whether a difference between the phase offset and a reference phase offset is less than a threshold difference, after correcting for phase wrapping differences.

18. The method of claim 11 , wherein determining whether the phase offset is consistent with the previous phase offset comprises generating a reference phase offset based on at least said previous phase offset.

19. The method of claim 18 , wherein calculating the average phase offset comprises adding the phase offset to an accumulator, and wherein generating the reference phase offset comprises averaging the accumulator contents only when a number of phase offsets accumulated in the accumulator is equal to two raised to an integer power.

20. A storage device, comprising:

a magnetic storage medium;

an array reader disposed in relation to the storage medium and operable to read and write data on the storage medium; and

a head separation calculation circuit operable to calculate an average phase offset between signals from read heads in the array reader, the head separation calculation circuit comprising:

means for calculating a phase offset as a difference between a phase of a first signal derived from a first read head in the array reader and a second phase of a second signal derived from a second read head in the array reader;

means for correcting for phase wrapping differences between the phase offset and a previous phase offset;

means for determining whether the phase offset is consistent with the previous phase offset; and

means for calculating an average phase offset which includes the phase offset only if it is consistent with the previous phase offset.

Assignments (8)