Detecting radial head position using spiral wedge information in self-servo-write
Writing servo wedge code to a disk is disclosed. A first selected burst demodulation window is determined. A final radial head position is computed based at least in part on the first selected burst demodulation window. Servo wedge code is written to a disk based at least in part on the final radial head position.
1. A method for writing servo wedge code to a disk, comprising:
determining a first selected burst demodulation window;
using a processor to compute a final radial head position based at least in part on the first selected burst demodulation window, wherein:
(1) the final radial head position is computed based at least in part on both the first selected burst demodulation window and a second selected burst demodulation window;
(2) the first selected burst demodulation window and the second selected burst demodulation window are associated with a first spiral burst amplitude and a second spiral burst amplitude, respectively, and the first spiral burst amplitude and the second spiral burst amplitude are adjacent to a central burst value; and
(3) the final radial head position is further computed at least in part by computing the difference between the first spiral burst amplitude and the central burst value; and
writing servo wedge code to a disk based at least in part on the final radial head position.
2. A method as recited in claim 1 , wherein computing the final radial head position further comprises:
computing a rough radial head position based at least in part on the first selected burst demodulation window;
computing a fine radial head position based at least in part on a second selected burst demodulation window; and
combining the rough radial head position and the final radial head position to obtain the final radial head position.
3. A method as recited in claim 2 , wherein combining the rough radial head position and the fine radial head position to obtain a final radial head position comprises summing the rough radial head position and the final radial head position to obtain the final radial head position.
4. A method as recited in claim 1 , wherein the final radial head position is computed based at least in part on an index of the first selected burst demodulation window.
5. A method as recited in claim 1 , wherein the first selected burst demodulation window is associated with a first spiral burst amplitude that is adjacent to a central burst value.
6. A method as recited in claim 1 , wherein the central burst value is selected from a linear portion of a radial burst amplitude curve.
7. A method as recited in claim 1 , wherein the final radial head position is computed based on no more than two burst demodulation windows.
8. A method as recited in claim 1 , wherein the final radial head position is computed based on no more than one half of one spiral segment.
9. A method as recited in claim 1 , wherein the final radial head position is computed based at least in part on a spiral offset value associated with a desired spiral segment used to detect the final radial head position.
10. A method as recited in claim 1 , wherein the first selected burst demodulation window changes depending on the radial position of the head.
11. A method as recited in claim 1 , wherein the first selected burst demodulation window includes a preamble waveform but not a sync mark waveform.
12. A method as recited in claim 1 , wherein computing the final radial head position includes computing an offset value between two spiral segments.
13. A method for writing servo wedge code to a disk, comprising:
determining a first selected burst demodulation window;
using a processor to compute a final radial head position based at least in part on the first selected burst demodulation window, wherein:
(1) the final radial head position is computed based at least in part on both the first selected burst demodulation window and a second selected burst demodulation window;
(2) the first selected burst demodulation window and the second selected burst demodulation window are associated with a first spiral burst amplitude and a second spiral burst amplitude, respectively, and the first spiral burst amplitude and the second spiral burst amplitude are adjacent to a central burst value; and
(3) the final radial head position is further computed at least in part by:
computing the difference between the first spiral burst amplitude and the second spiral burst amplitude; and
taking the absolute value of the difference between the first spiral burst amplitude and the second spiral burst amplitude; and
writing servo wedge code to a disk based at least in part on the final radial head position.
14. A method for writing servo wedge code to a disk, comprising:
determining a first selected burst demodulation window;
using a processor to compute a final radial head position based at least in part on the first selected burst demodulation window;
writing servo wedge code to a disk based at least in part on the final radial head position; and
calibrating a center burst value at least in part by displacing a head and determining whether there is a discontinuity.
15. A method for writing servo wedge code to a disk, comprising:
determining a first selected burst demodulation window;
using a processor to compute a final radial head position based at least in part on the first selected burst demodulation window;
writing servo wedge code to a disk based at least in part on the final radial head position; and
calibrating a window radial distance at least in part by displacing a head and determining a difference in spiral burst amplitude.
16. A system for writing servo wedge code to a disk, comprising:
a processor configured to:
determine a first selected burst demodulation window;
compute a final radial head position based at least in part on the first selected burst demodulation window, wherein:
(1) the final radial head position is computed based at least in part on both the first selected burst demodulation window and a second selected burst demodulation window;
(2) the first selected burst demodulation window and the second selected burst demodulation window are associated with a first spiral burst amplitude and a second spiral burst amplitude, respectively, and the first spiral burst amplitude and the second spiral burst amplitude are adjacent to a central burst value; and
(3) the final radial head position is further computed at least in part by computing the difference between the first spiral burst amplitude and the central burst value; and
write servo wedge code to a disk based at least in part on the final radial head position; and
a communication interface coupled to the processor.
17. A system as recited in claim 16 , wherein the processor is configured to compute the final radial head position at least in part by:
computing a rough radial head position based at least in part on the first selected burst demodulation window;
computing a fine radial head position based at least in part on a second selected burst demodulation window; and
combining the rough radial head position and the final radial head position to obtain the final radial head position.
18. A system for writing servo wedge code to a disk, comprising:
a processor configured to:
determine a first selected burst demodulation window;
compute a final radial head position based at least in part on the first selected burst demodulation window, wherein:
(1) the final radial head position is computed based at least in part on both the first selected burst demodulation window and a second selected burst demodulation window;
(2) the first selected burst demodulation window and the second selected burst demodulation window are associated with a first spiral burst amplitude and a second spiral burst amplitude, respectively, and the first spiral burst amplitude and the second spiral burst amplitude are adjacent to a central burst value; and
(3) the final radial head position is further computed at least in part by:
computing the difference between the first spiral burst amplitude and the second spiral burst amplitude; and
taking the absolute value of the difference between the first spiral burst amplitude and the second spiral burst amplitude; and
write servo wedge code to a disk based at least in part on the final radial head position; and
a communication interface coupled to the processor.
19. A system for writing servo wedge code to a disk, comprising:
a processor configured to:
determine a first selected burst demodulation window;
compute a final radial head position based at least in part on the first selected burst demodulation window;
write servo wedge code to a disk based at least in part on the final radial head position; and
calibrate a center burst value at least in part by displacing a head and determining whether there is a discontinuity; and
a communication interface coupled to the processor.
20. A system for writing servo wedge code to a disk, comprising:
a processor configured to:
determine a first selected burst demodulation window;
compute a final radial head position based at least in part on the first selected burst demodulation window;
write servo wedge code to a disk based at least in part on the final radial head position; and
calibrate a window radial distance at least in part by displacing a head and determining a difference in spiral burst amplitude; and
a communication interface coupled to the processor.