Data storage device comprising equalizer filter and inter-track interference filter

• US 8,947,812 B1
• Filed: 03/27/2014
• Issued: 02/03/2015
• Est. Priority Date: 03/27/2014
• Status: Active Grant

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: Wang, Alvin J.
• Primary Examiner(s): Edun, Muhammad N
• Application Number:
  US14/227,896
• Time in Patent Office: 313 Days
• Field of Search: None
• US Class Current: 360/53
• CPC Class Codes: G11B 20/10046 filtering or equalising, e.g. setting the tap weights of an FIR filter
• 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
• CPC Class Codes: G11B 5/09 Digital recording
• CPC Class Codes: G11B 5/59622 Gain control; Filters
• CPC Class Codes: G11B 5/59688 Servo signal format patterns or signal processing thereof, e.g. dual, tri, quad, burst signal patterns

Abstract

A data storage device is disclosed comprising a head actuated over a disk. A read signal from the head is sampled to generate signal samples, and the signal samples are filtered with an equalizer filter to generate equalized samples. The equalized samples are filtered with an inter-track interference (ITI) filter to generate ITI attenuated samples, and a data sequence is detected based on the ITI attenuated samples. In one embodiment, the ITI filter comprises a transfer function:
1−HPF(e_k)
and in another embodiment the ITI filter comprises a transfer function:
1−LPF(e_k)
where e_k represents a noise sequence in the equalized samples, HPF represents a high pass filter operating on e_k, and LPF represents a low pass filter operating on e_k.

Claims

1. A data storage device comprising:

a disk;

a head actuated over the disk; and

control circuitry configured to;

sample a read signal from the head to generate signal samples;

filter the signal samples with an equalizer filter to generate equalized samples;

filter the equalized samples with an inter-track interference (ITI) filter to generate ITI attenuated samples; and

detect a data sequence based on the ITI attenuated samples,

wherein the ITI filter comprises a transfer function;

1−

HPF(e_k)

where;

e_k represents a noise sequence in the equalized samples; and

HPF represents a high pass filter operating on e_k.

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

y_k=α

e_k−

(α

e_k-1+β

y_k-1)

where;

y_k represents an output of the HPF; and

α and

β

are coefficients.

3. The data storage device as recited in claim 2, where α

and β

are programmable coefficients.

4. The data storage device as recited in claim 1, where the control circuitry is further configured to generate the noise sequence by computing a difference between the equalized samples and corresponding ideal samples.

5. The data storage device as recited in claim 4, where the control circuitry is further configured to generate the ideal samples based on the detected data sequence.

6. The data storage device as recited in claim 4, where the control circuitry is further configured to generate the ideal samples based on a test pattern written to the disk.

7. A data storage device comprising:

a disk;

a head actuated over the disk; and

control circuitry configured to;

sample a read signal from the head to generate signal samples;

filter the signal samples with an equalizer filter to generate equalized samples;

filter the equalized samples with an inter-track interference (ITI) filter to generate ITI attenuated samples; and

detect a data sequence based on the ITI attenuated samples,

wherein the ITI filter comprises a transfer function;

1−

LPF(e_k)

where;

e_k represents a noise sequence in the equalized samples; and

LPF represents a low pass filter operating on e_k.

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

y_k=α

(e_k+β

e_k-1)

where;

y_k represents an output of the LPF; and

α and

β

are coefficients.

9. The data storage device as recited in claim 8, where α

and β

are programmable coefficients.

10. The data storage device as recited in claim 7, where the control circuitry is further configured to generate the noise sequence by computing a difference between the equalized samples and corresponding ideal samples.

11. The data storage device as recited in claim 10, where the control circuitry is further configured to generate the ideal samples based on the detected data sequence.

12. The data storage device as recited in claim 10, where the control circuitry is further configured to generate the ideal samples based on a test pattern written to the disk.

13. A method of operating a data storage device, the method comprising:

sampling a read signal from a head actuated over a disk to generate signal samples;

filtering the signal samples with an equalizer filter to generate equalized samples;

filtering the equalized samples with an inter-track interference (ITI) filter to generate ITI attenuated samples; and

detecting a data sequence based on the ITI attenuated samples,

wherein the ITI filter comprises a transfer function;

1−

HPF(e_k)

where;

e_k represents a noise sequence in the equalized samples; and

HPF represents a high pass filter operating on e_k.

14. The method device as recited in claim 13, wherein the HPF comprises a form:

y_k=α

e_k−

(α

e_k-1+β

y_k-1)

where;

y_k represents an output of the HPF; and

α and

β

are coefficients.

15. The method as recited in claim 14, where α

and β

are programmable coefficients.

16. The method as recited in claim 13, further comprising generating the noise sequence by computing a difference between the equalized samples and corresponding ideal samples.

17. The method as recited in claim 16, further comprising generating the ideal samples based on the detected data sequence.

18. The method as recited in claim 16, further comprising generating the ideal samples based on a test pattern written to the disk.

19. A method of operating a data storage device, the method comprising:

sampling a read signal from a head actuated over a disk to generate signal samples;

filtering the signal samples with an equalizer filter to generate equalized samples;

filtering the equalized samples with an inter-track interference (ITI) filter to generate ITI attenuated samples; and

detecting a data sequence based on the ITI attenuated samples,

wherein the ITI filter comprises a transfer function;

1−

LPF(e_k)

where;

e_k represents a noise sequence in the equalized samples; and

LPF represents a low pass filter operating on e_k.

20. The method as recited in claim 19, wherein the LPF comprises a form:

y_k=α

(e_k+β

e_k-1)

where;

y_k represents an output of the LPF; and

α and

β

are coefficients.

21. The method as recited in claim 20, where α

and β

are programmable coefficients.

22. The method as recited in claim 19, further comprising generating the noise sequence by computing a difference between the equalized samples and corresponding ideal samples.

23. The method as recited in claim 22, further comprising generating the ideal samples based on the detected data sequence.

24. The method as recited in claim 22, further comprising generating the ideal samples based on a test pattern written to the disk.