Data storage device comprising sequence detector compensating for inter-track interference

• US 9,257,146 B1
• Filed: 02/11/2014
• Issued: 02/09/2016
• Est. Priority Date: 02/11/2014
• Status: Active Grant

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: Wang, Alvin J., Dahandeh, Shafa
• Primary Examiner(s): HOLDER, REGINA NEAL
• Application Number:
  US14/178,155
• Time in Patent Office: 728 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G11B 20/10046 filtering or equalising, e.g. setting the tap weights of an FIR filter
• CPC Class Codes: G11B 20/10055 using partial response filtering when writing the signal to the medium or reading it therefrom
• CPC Class Codes: G11B 20/10268 bit detection or demodulation methods
• CPC Class Codes: G11B 20/10277 the demodulation process being specifically adapted to partial response channels, e.g. PRML decoding

Abstract

A data storage device is disclosed comprising a head actuated over a disk comprising a plurality of data tracks. A first data track is read to generate a first read signal, the first read signal is sampled to generate first read signal samples, a first data sequence is detected based on the first read signal samples, and the first data sequence is converted into corresponding first expected samples. A second data track adjacent the first data track is read to generate a second read signal, the second read signal is sampled to generate second read signal samples, and a second data sequence is detected based on the second read signal samples and the first expected samples.

Claims

1. A data storage device comprising:

a disk comprising a plurality of data tracks;

a head actuated over the disk; and

control circuitry configured to;

read a first data track to generate a first read signal;

sample the first read signal to generate first read signal samples;

detect a first data sequence based on the first read signal samples;

filter the first data sequence with a target partial response to convert the first data sequence into corresponding first expected samples;

read a second data track adjacent the first data track to generate a second read signal;

sample the second read signal to generate second read signal samples; and

detect a second data sequence based on the second read signal samples and the first expected samples.

2. The data storage device as recited in claim 1, wherein the head comprises:

a first read element for positioning over the first data track to generate the first read signal; and

a second read element for positioning over the second data track to generate the second read signal.

3. The data storage device as recited in claim 2, wherein the control circuitry is configured to generate the first read signal and the second read signal during a single revolution of the disk.

4. The data storage device as recited in claim 2, wherein the control circuitry is further configured to:

detect the first data sequence using a downtrack interference (DTI) trellis type sequence detector; and

detect the second data sequence using a DTI and intertrack interference (ITI) trellis type sequence detector.

5. The data storage device as recited in claim 4, wherein the DTI and ITI trellis type sequence detector is configured to generate a branch metric of a trellis based on at least one of the first expected samples and a DTI expected sample.

6. The data storage device as recited in claim 5, wherein the control circuitry is further configured to:

scale the at least one of the first expected samples to generate a scaled expected sample; and

generate the branch metric of a trellis based on the scaled expected sample and the DTI expected sample.

7. The data storage device as recited in claim 1, wherein the control circuitry is further configured to:

read a third data track adjacent the first data track to generate a third read signal;

sample the third read signal to generate third read signal samples;

detect a third data sequence based on the third read signal samples;

convert the third data sequence into corresponding second expected samples; and

detect the second data sequence based on the second read signal samples, the first expected samples, and the second expected samples.

8. The data storage device as recited in claim 7, wherein the head comprises:

a first read element for positioning over the first data track to generate the first read signal;

a second read element for positioning over the second data track to generate the second read signal; and

a third read element for positioning over the third data track to generate the third read signal.

9. The data storage device as recited in claim 8 wherein the control circuitry is configured to generate the first read signal, the second read signal, and the third read signal during a single revolution of the disk.

10. The data storage device as recited in claim 1, wherein the control circuitry is further configured to:

read the first data track to generate the first read signal and detect the first data sequence during a first revolution of the disk;

store the first data sequence; and

read the second data track to generate the second read signal and detect the second data sequence during a second revolution of the disk based on the stored first data sequence.

11. The data storage device as recited in claim 1, wherein the control circuitry is further configured to detect the second data sequence using a downtrack interference (DTI) and intertrack interference (ITI) trellis type sequence detector.

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

reading a first data track of a disk to generate a first read signal;

sampling the first read signal to generate first read signal samples;

detecting a first data sequence based on the first read signal samples;

filtering the first data sequence with a target partial response to convert the first data sequence into corresponding first expected samples;

reading a second data track of the disk adjacent the first data track to generate a second read signal;

sampling the second read signal to generate second read signal samples; and

detecting a second data sequence based on the second read signal samples and the first expected samples.

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

positioning a first read element over the first data track to generate the first read signal; and

positioning a second read element over the second data track to generate the second read signal.

14. The method as recited in claim 13, further comprising generating the first read signal and the second read signal during a single revolution of the disk.

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

detecting the first data sequence using a downtrack interference (DTI) trellis type sequence detector; and

detecting the second data sequence using a DTI and intertrack interference (ITI) trellis type sequence detector.

16. The method as recited in claim 15, wherein the DTI and ITI trellis type sequence detector is configured to generate a branch metric of a trellis based on at least one of the first expected samples and a DTI expected sample.

17. The method as recited in claim 16, further comprising:

scaling the at least one of the first expected samples to generate a scaled expected sample; and

generating the branch metric of a trellis based on the scaled expected sample and the DTI expected sample.

18. The method as recited in claim 16, further comprising:

reading a third data track of the disk adjacent the first data track to generate a third read signal;

sampling the third read signal to generate third read signal samples;

detecting a third data sequence based on the third read signal samples;

converting the third data sequence into corresponding second expected samples; and

detecting the second data sequence based on the second read signal samples, the first expected samples, and the second expected samples.

19. The method as recited in claim 18, further comprising:

positioning a first read element over the first data track to generate the first read signal;

positioning a second read element over the second data track to generate the second read signal; and

positioning a third read element over the third data track to generate the third read signal.

20. The method as recited in claim 19, further comprising generating the first read signal, the second read signal, and the third read signal during a single revolution of the disk.

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

reading the first data track to generate the first read signal and detect the first data sequence during a first revolution of the disk;

storing the first data sequence; and

reading the second data track to generate the second read signal and detect the second data sequence during a second revolution of the disk based on the stored first data sequence.

22. The method as recited in claim 12, further comprising detecting the second data sequence using a downtrack interference (DTI) and intertrack interference (ITI) trellis type sequence detector.

23. Control circuitry configured to:

read a first data track of a disk to generate a first read signal;

sample the first read signal to generate first read signal samples;

detect a first data sequence based on the first read signal samples;

filter the first data sequence with a target partial response to convert the first data sequence into corresponding first expected samples;

read a second data track of the disk adjacent the first data track to generate a second read signal;

sample the second read signal to generate second read signal samples; and

detect a second data sequence based on the second read signal samples and the first expected samples.