Phase Servo Patterns for Bit Patterned Media

• US 20100067142A1
• Filed: 09/15/2008
• Published: 03/18/2010
• Est. Priority Date: 09/15/2008
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Pokharel, Puskal Prasad, Ozturk, Mustafa Can
• Granted Patent: US 7,920,354 B2
• Time in Patent Office: Days
• US Class Current: 360/77.80
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: G11B 5/59688 Servo signal format patterns or signal processing thereof, e.g. dual, tri, quad, burst signal patterns
• CPC Class Codes: G11B 5/743 Patterned record carriers, wherein the magnetic recording layer is patterned into magnetic isolated data islands, e.g. discrete tracks
• CPC Class Codes: G11B 5/82 Disk carriers

Abstract

A recordable medium according to some embodiments includes a servo control field having a bit patterned media (BPM) pattern. The pattern includes a plurality of isolated magnetic islands or dots arranged in a down-track orientation and in a cross-track orientation. A phase of dots arranged on the medium in the servo control field varies in a first cross-track direction. The dots arranged on the medium may include a first phase pattern that has a first phase gradient in the first cross-track direction and a second phase pattern that has a second phase gradient, different from the first phase gradient, in the first cross-track direction. The dots may include a plurality of dot composites including a plurality of dots.

Claims

1. A recordable medium, comprising:

a servo control field comprising a bit patterned media (BPM) pattern including a plurality of dots arranged in a down-track orientation and in a cross-track orientation, wherein a phase of dots arranged on the medium in the servo control field varies in a cross-track direction.

2. The recordable medium of claim 1, wherein the dots arranged on the medium comprise a first phase pattern that has a first phase gradient in a first cross-track direction and a second phase pattern that has a second phase gradient, different from the first phase gradient, in the first cross-track direction.

3. The recordable medium of claim 2, wherein the first phase gradient is positive in the first cross-track direction and the second phase gradient is negative in the first cross-track direction.

4. The recordable medium of claim 1, wherein the phase of dots in the first phase pattern varies monotonically in the cross-track direction.

5. The recordable medium of claim 1, wherein the dots comprise a plurality of dot composites, each of the dot composites including a plurality of dots, wherein a first spacing between adjacent ones of the plurality of dots in a dot composite is less than a second spacing between adjacent ones of the plurality of dot composites.

6. The recordable medium of claim 5, wherein the first spacing is zero.

7. The recordable medium of claim 5, wherein an aspect ratio of the dots changes in a cross-track and/or a down-track direction.

8. The recordable medium of claim 5, wherein an aspect ratio of the dots and a number of dots in a dot composite changes in a cross-track direction.

9. The recordable medium of claim 1, wherein an aspect ratio of the dots changes in a cross-track direction.

10. The recordable medium of claim 1, wherein the dots are arranged in the down-track direction with a periodicity of p, each row of dots forms a subtrack of a disk track having n_s subtracks, and the phase of dots in the first phase pattern varies by 360 degrees per n tracks so that each successive subtrack is shifted in a down-track direction by a distance of p/(n*ns) with respect to the previous subtrack.

11. The recordable medium of claim 1, wherein the dots in the servo control field are DC erased to have a single magnetization polarity.

12. The recordable medium of claim 1, wherein the servo control field comprises a servo burst field.

13. A recordable medium, comprising:

a servo control field comprising a bit patterned media (BPM) pattern including a plurality of dots arranged in a down-track direction and in a cross-track direction, wherein a phase of dots arranged on the medium in the servo control field varies in the cross-track direction; and

wherein the dots comprise a plurality of dot composites, each of the dot composites including a plurality of dots.

14. The recordable medium of claim 13, wherein a first spacing between adjacent ones of the plurality of dots in a dot composite is less than a second spacing between adjacent ones of the plurality of dot composites.

15. The recordable medium of claim 14, wherein the first spacing is zero.

16. The recordable medium of claim 13, wherein an aspect ratio of the dots changes in a cross-track direction.

17. The recordable medium of claim 13, wherein an aspect ratio of the dots and a number of dots in a dot composite changes in a cross-track direction.

18. A servo control system, comprising:

a recordable medium comprising a servo control field comprising a bit patterned media (BPM) pattern, the BPM pattern including a plurality of dots arranged in a down-track direction in a cross-track direction, wherein a phase of dots arranged on the medium in the servo control field varies in the cross-track direction and wherein the dots comprise a plurality of dot composites, each of the dot composites including a plurality of dots;

a transducer that generates a readback signal in response to a magnetic field generated by the dots; and

a controller that controls a position of the transducer in response to a readback signal from the transducer.

19. The servo control system of claim 18, wherein a first spacing between adjacent ones of the plurality of dots in a dot composite is less than a second spacing between adjacent ones of the plurality of dot composites.

20. The servo control system of claim 18, wherein the first spacing is zero.

21. The servo control system of claim 18, wherein the dots arranged on the medium comprise a first phase pattern that has a positive phase gradient in the first cross-track direction and a second phase pattern that has a negative phase gradient in the first cross-track direction.

22. The servo control system of claim 18, wherein the dots are arranged in the down-track direction with a periodicity of p, each row of dots forms a subtrack of a disk track having n_s subtracks, and the phase of dots in the first phase pattern varies by 360 degrees per n tracks so that each successive subtrack is shifted in a down-track direction by a distance of p/(n*ns) with respect to the previous subtrack.