Data storage device comprising dual read sensors and dual servo channels to improve servo demodulation
View Patent ↗A data storage device is disclosed comprising a disk comprising a plurality of servo tracks defined by servo sectors, wherein each servo sector comprises a plurality of servo bursts. A head comprises a first read sensor and a second read sensor separated from the first read sensor by a cross-track spacing. A first servo channel processes a first read signal emanating from the first read sensor to generate a first position signal based on at least two servo bursts read using the first read sensor. A second servo channel processes a second read signal emanating from the second read sensor to generate a second position signal based on at least two servo bursts read using the second read sensor. A position error signal (PES) is generated based on the first position signal and the second position signal, and the head is servoed over the disk based on the PES.
1. A data storage device comprising:
a disk comprising a plurality of servo tracks defined by servo sectors, wherein each servo sector comprises a plurality of servo bursts;
a head comprising a plurality of read sensors including a first read sensor, and a second read sensor separated from the first read sensor by a cross-track spacing;
a first servo channel configured to process a first read signal emanating from the first read sensor to generate a first position signal based on at least two servo bursts read using the first read sensor;
a second servo channel configured to process a second read signal emanating from the second read sensor to generate a second position signal based on at least two servo bursts read using the second read sensor; and
control circuitry configured to:
generate a position error signal (PES) based on the first position signal and the second position signal; and
servo the head over the disk based on the PES.
2. The data storage device as recited in claim 1 , wherein:
each servo sector comprises a track ID;
the first servo channel is configured to generate the first position signal based on a track ID; and
the second servo channel is configured to generate the second position signal based on a track ID.
3. The data storage device as recited in claim 1 , wherein:
the first servo channel comprises a first sync mark detector configured to generate a first sync mark signal based on the first read signal;
the second servo channel comprises a second sync mark detector configured to generate a second sync mark signal based on the second read signal; and
the control circuitry is configured to synchronize to a servo sector based on the first sync mark signal and the second sync mark signal.
4. The data storage device as recited in claim 3 , wherein:
each servo sector comprises a servo sync mark;
the first sync mark detector is configured to generate the first sync mark signal based on a servo sync mark; and
the second sync mark detector is configured to generate the second sync mark signal based on a servo sync mark.
5. The data storage device as recited in claim 3 , wherein:
each servo sector comprises a servo sync mark and servo data; and
the first sync mark detector is configured to generate the first sync mark signal based on a first plurality of bits of the servo data of a servo sector.
6. The data storage device as recited in claim 5 , wherein the second sync mark detector is configured to generate the second sync mark signal based on a second plurality of bits of the servo data of a servo sector.
7. The data storage device as recited in claim 6 , wherein:
the first plurality of bits of the servo data comprises at least two bits of a wedge ID; and
the second plurality of bits of the servo data comprises at least two bits of a track ID.
8. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to measure the cross-track spacing based on the first position signal and the second position signal.
9. The data storage device as recited in claim 1 , wherein:
the first servo sector comprises a first track ID;
the second servo sector comprises a second track ID;
the first servo channel comprises a first track ID detector configured to generate a first detected track ID;
the second servo channel comprises a second track ID detector configured to generate a second detected track ID; and
the control circuitry is further configured to detect an error in at least one of the first detected track ID and the second detected track ID based on the cross-track spacing between the first and second read sensors.
10. The data storage device as recited in claim 9 , wherein the control circuitry is further configured to correct the error based on a proximity of at least one of the first detected track ID and the second detected track ID to at least one estimated track ID.
11. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to:
measure the cross-track spacing between the first and second read sensors; and
generate the PES based on the measured cross-track spacing.
12. The data storage device as recited in claim 1 , wherein the head comprises a third read sensor fabricated between the first read sensor and the second read sensor along a cross-track direction such that a cross-track spacing between the first and second read sensors is greater than a cross-track spacing between the first read sensor and the third read sensor.
13. The data storage device as recited in claim 1 , wherein the cross-track spacing between the first read sensor and the second read sensor comprises at least one servo track.
14. A method of operating a data storage device, the method comprising:
processing a first read signal emanating from a first read sensor of a head to generate a first position signal based on at least two servo bursts read using the first read sensor;
processing a second read signal emanating from a second read sensor of the head to generate a second position signal based on at least two servo bursts read using the second read sensor;
generating a position error signal (PES) based on the first position signal and the second position signal; and
servoing the head over the disk based on the PES.
15. The method as recited in claim 14 , further comprising:
generating the first position signal based on a track ID; and
generating the second position signal based on a track ID.
16. The method as recited in claim 14 , further comprising:
generating a first sync mark signal based on the first read signal;
generating a second sync mark signal based on the second read signal; and
synchronizing to a servo sector based on the first sync mark signal and the second sync mark signal.
17. The method as recited in claim 16 , further comprising generating the first sync mark signal based on a first plurality of bits of servo data of a servo sector.
18. The method as recited in claim 17 , further comprising generating the second sync mark signal based on a second plurality of bits of servo data of a servo sector.
19. The method as recited in claim 18 , wherein:
the first plurality of bits of the servo data comprises at least two bits of a wedge ID; and
the second plurality of bits of the servo data comprises at least two bits of a track ID.
20. The method as recited in claim 14 , further comprising measuring a cross-track spacing between the first and second read sensors based on the first position signal and the second position signal.
21. The method as recited in claim 14 , further comprising:
generating a first detected track ID;
generating a second detected track ID; and
detecting an error in at least one of the first detected track ID and the second detected track ID based on a cross-track spacing between the first and second read sensors.
22. The method as recited in claim 21 , further comprising correcting the error based on a proximity of at least one of the first detected track ID and the second detected track ID to at least one estimated track ID.
23. The method as recited in claim 14 , further comprising:
measuring the cross-track spacing between the first and second read sensors; and
generating the PES based on the measured cross-track spacing.
24. The method as recited in claim 14 , wherein the head comprises a third read sensor fabricated between the first read sensor and the second read sensor along a cross-track direction such that a cross-track spacing between the first and second read sensors is greater than a cross-track spacing between the first read sensor and the third read sensor.
25. The method as recited in claim 14 , wherein a cross-track spacing between the first read sensor and the second read sensor comprises at least one servo track.