received by the International Bureau on

03 APRIL 2015

(03.04.2015)

1. A hard disk drive circuit comprising:

a first inter-track interference detection module configured to generate a first measured inter-track interference value based on a first read signal from a first read sensor positioned over a first track of a magnetic medium, wherein the first measured inter-track interference value indicates an amount of energy contributed to the first read signal by tracks adjacent to the first track compared to an amount of energy contributed to the first read signal by the first track;

a second inter-track interference detection module configured to generate a second measured inter-track interference value based on a second read signal from a second read sensor positioned over a second track of the magnetic medium, wherein the second measured inter-track interference value indicates an amount of energy contributed to the second read signal by tracks adjacent to the second track compared to an amount of energy contributed to the second read signal by the second track;

a position error signal generation module configured to generate a position error signal based on the first measured inter-track interference value and the second measured inter-track interference value; and

an arm control module configured to control rotation of an arm in response to the position error signal, wherein the first read sensor and the second read sensor are located at a distal end of the arm.

2. A hard disk drive system comprising:

the hard disk drive circuit of claim 1; and

a hard disk assembly comprising a read head, wherein the read head includes the first read sensor and the second read sensor.

3. The hard disk drive system of claim 2, further comprising a voice coil motor configured to rotate the arm in response to the arm control module.

4. The hard disk drive circuit of claim 1, wherein:

the first inter-track interference detection module is configured to generate the first measured inter-track interference value while the first read sensor is positioned over first preamble data; and

the second inter-track interference detection module is configured to generate the second measured inter-track interference value while the second read sensor is positioned over second preamble data.

5. The hard disk drive circuit of claim 4, wherein alternating tracks of the magnetic medium include orthogonal preambles.

6. The hard disk drive circuit of claim 1, wherein the position error signal generation module is configured to generate the position error signal based on (i) a first difference between the first measured inter-track interference value and a first target inter-track interference value and (ii) a second difference between the second measured inter-track interference value and a second target inter-track interference value.

7. The hard disk drive circuit of claim 6, wherein the position error signal generation module is configured to generate the position error signal based on an average of the first difference and the second difference.

8. The hard disk drive circuit of claim 6, further comprising an offset calibration module configured to specify the first target inter-track interference value and the second target inter-track interference value in response to a number, wherein the number identifies which track of the magnetic medium is being read by the hard disk drive circuit.

9. The hard disk drive circuit of claim 1, further comprising an offset calibration module configured to specify an offset between the first read sensor and the second read sensor in response to a number, wherein the number identifies which track of the magnetic medium is being read by the hard disk drive circuit.

10. The hard disk drive circuit of claim 9, wherein the position error signal generation module is configured to determine a sign of the position error signal based on the offset.

11. The hard disk drive circuit of claim 1, further comprising:

an inter-track interference cancellation module configured to generate a read signal based on the first read signal and the second read signal; and

a delay module configured to delay the second read signal, wherein the inter-track interference cancellation module operates using the delayed second read signal instead of the second read signal.

12. The hard disk drive circuit of claim 1, further comprising a third inter-track interference detection module configured to generate a third measured inter-track interference value based on a third read signal from a third read sensor positioned over the magnetic medium, wherein the position error signal generation module is configured to generate the position error signal based on the first measured inter-track interference value, the second measured inter-track interference value, and the third measured inter- track interference value.

13. A method of operating a hard disk drive circuit, the method comprising:

generating a first measured inter-track interference value based on a first read signal from a first read sensor positioned over a first track of a magnetic medium, wherein the first measured inter-track interference value indicates an amount of energy contributed to the first read signal by tracks adjacent to the first track compared to an amount of energy contributed to the first read signal by the first track;

generating a second measured inter-track interference value based on a second read signal from a second read sensor positioned over a second track of the magnetic medium, wherein the second measured inter-track interference value indicates an amount of energy contributed to the second read signal by tracks adjacent to the second track compared to an amount of energy contributed to the second read signal by the second track;

generating a position error signal based on the first measured inter-track interference value and the second measured inter-track interference value; and

controlling rotation of an arm in response to the position error signal, wherein the first read sensor and the second read sensor are located at a distal end of the arm.

14. The method of claim 13, wherein:

the generating the first measured inter-track interference value is performed while the first read sensor is positioned over first preamble data; and

the generating the second measured inter-track interference value is performed while the second read sensor is positioned over second preamble data.

15. The method of claim 14, wherein alternating tracks of the magnetic medium include orthogonal preambles.

16. The method of claim 13, wherein the position error signal is generated based on (i) a first difference between the first measured inter-track interference value and a first target inter-track interference value and (ii) a second difference between the second measured inter-track interference value and a second target inter-track interference value.

17. The method of claim 16, wherein the position error signal is generated based on an average of the first difference and the second difference.

18. The method of claim 16, further comprising specifying the first target inter-track interference value and the second target inter-track interference value in response to a number, wherein the number identifies which track of the magnetic medium is being read by the hard disk drive circuit.

19. The method of claim 13, further comprising specifying an offset between the first read sensor and the second read sensor in response to a number, wherein the number identifies which track of the magnetic medium is being read by the hard disk drive circuit.

20. The method of claim 19, further comprising determining a sign of the position error signal based on the offset.