Bit patterned medium, reading head for reading data recorded on bit patterned medium, and hard disk drive for recording/reading data on/from bit patterned medium
View Patent ↗Provided are a bit patterned medium having a super track, a reading head which reads data recorded on the bit-patterned medium, and a hard disk drive (HDD) for recording/reading data on/from the bit patterned medium. The bit patterned medium includes a substrate, and a recording layer formed with a plurality of bit cells separated from each other along a plurality of tracks forming concentric circles having different radii on the substrate, wherein each track includes a super track including a plurality of sub-tracks, and bit cells formed on one of the sub-tracks are arranged at different positions in a circumference direction of the recording layer to bit cells formed on adjacent sub-tracks. The reading head which reads data recorded on a bit patterned medium has a width in a cross-track direction sufficient for reading data of an equal number of bit cells as the plurality of sub-tracks.
1. A bit patterned medium comprising:
a substrate; and
a recording layer including a plurality of bit cells separated from each other along a plurality of tracks forming concentric circles having different radii on the substrate,
wherein each track includes a super track having a plurality of sub-tracks, and bit cells formed on one of the sub-tracks are arranged at different positions in a circumference direction of the recording layer to bit cells formed on adjacent sub-tracks,
wherein if a number of the plurality of sub-tracks is N,
N bit cells are arranged adjacent to each other in a radius direction of the super track to cause interference of a reproduction signal due to bit cell data of each bit cell of the N bit cells, and
when the bit cell data stored in the N bit cells is simultaneously read, an interval X between every two adjacent bit cells of the N bit cells in the circumference direction is determined so that at a predetermined position corresponding to one bit cell of the N bit cells, 2 N reproduction signal values from respective combinations of the bit cell data stored in the N bit cells are all different.
2. The bit patterned medium of claim 1 , wherein the interval X is determined so that the 2 N reproduction signals have an equal interval value.
3. The bit patterned medium of claim 2 , wherein when N is 2, the interval X satisfies an equation
f (φ)=2 f (φ−X),
where f(φ) is a reproduction signal generated from the bit cell data stored in a bit cell of the N bit cells, as a function of a coordinate value φindicating a position in the circumference direction.
4. The bit patterned medium of claim 1 , wherein an interval between every two adjacent bit cells in the circumference direction is equal in each sub-track.
5. The bit patterned medium of claim 4 , wherein a circumference-directional length of each bit cell is equal in each sub-track.
6. The bit patterned medium of claim 5 , wherein if a number of the plurality of sub-tracks is N and the circumference-directional length is Δφ ,
a circumference-directional interval between adjacent bit cells in a radius direction is formed as Δφ /N.
7. The bit patterned medium of claim 6 , wherein the circumference-directional interval between bit cells adjacent in the circumference direction is equal to or greater than 2Δφ.
8. The bit patterned medium of claim 1 , wherein the recording layer includes a magnetic material.
9. The bit patterned medium of claim 8 , wherein the recording layer further includes a material comprising at least one of Co, Fe, Pt and Pd.
10. The bit patterned medium of claim 1 , wherein the recording layer includes a ferroelectric material.
11. A bit cell arrangement method of a bit patterned medium including a substrate and a recording layer having a plurality of bit cells separated from each other along a plurality of tracks forming concentric circles having different radii on the substrate, wherein each track includes a super track having a plurality of sub-tracks, and bit cells formed on one of the sub-tracks are arranged at different positions in a circumference direction of the recording layer to bit cells formed on adjacent sub-tracks, the method comprising:
if the number of the plurality of sub-tracks is N, arranging N bit cells adjacent to each other in a radius direction in the super track to cause interference of a reproduction signal due to data of each bit cell; and
when data stored in the N bit cells is simultaneously read, determining an interval X between every two adjacent bit cells in a circumference direction so that at a predetermined position corresponding to one bit cell of the N bit cells, 2 N reproduction signals from respective combinations of the data stored in the N bit cells are all different.
12. A reading head which reads bit patterned medium data recorded on the bit patterned medium of claim 1 , wherein the reading head has a width in a cross-track direction sufficient for reading bit cell data of an equal number of bit cells as a number of the plurality of sub-tracks, at once.
13. The reading head of claim 12 , wherein the width of the reading head in the cross-track direction is equal to or less than a width of the super track.
14. The reading head of claim 12 , wherein the reading head is configured to use a magnetic field to record and reproduce the bit patterned medium data.
15. The reading head of claim 12 , wherein the reading head is configured to use an electric field to record and reproduce the bit patterned medium data.
16. A hard disk drive (HDD) comprising:
the bit patterned medium of claim 1 ;
a head unit including a recording head which records, on a super track basis, super track data on the super track of the bit patterned medium and a reading head which reads, on a super track basis, the super track data recorded on the super track of the bit patterned medium;
a head driver which drives the head unit; and
a reading channel circuit which separately extracts sub-track data of each of the plurality of sub-tracks from a reproduction signal with the super track data of the super track read by the reading head.
17. The HDD of claim 16 , wherein a width of the reading head in a cross-track direction is equal to or less than a width of the super track.
18. The HDD of claim 16 , wherein the head unit is configured to use a magnetic field to record and reproduce the super track data.
19. The HDD of claim 16 , wherein the head unit is configured to use an electric field to record and reproduce the super track data.
20. The HDD of claim 16 , wherein the head driver drives the head unit so that the reading head reads the super track data along a centerline of the super track.
21. The HDD of claim 16 , wherein if the super track data read from the super track includes bit cell data of N bit cells, the reading channel circuit separates the bit cell data of each bit cell of the of N bit cells from a reproducing signal at a sampling position at which 2 N reproduction signals from combinations of the bit cell data stored in the N bit cells have an equal interval value.
22. The HDD of claim 21 , wherein when a plurality of sampling positions exist,
the bit cell data of each bit cell of the of N bit cells is separated from a value obtained by operating reproduction signals at the plurality of sampling positions.