Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
2001-12-13
2004-07-20
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S077080, C360S053000, C360S077050, C360S078140
Reexamination Certificate
active
06765748
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of embedding interleaved servo information fields onto a disk used as a storage medium for a disk drive, and a disk having interleaved servo information fields embedded thereon for use as a storage medium for a disk drive.
2. Description of the Related Art
Disks used as storage mediums for conventional disk drive assemblies typically have embedded sector servo position information inserted thereon for closed loop GMR (giant magnetoresistive) head or MR (magnetoresistive) head position control. The embedded sector servo position information fields include information that generally provides timing reference, track identification, and fine track burst information. The head position system controls the position of the head carrier within the disk drive assembly, so that the read and write heads stay on the desired data track of the disk to read and write data accurately. The sector servo position information fields are exclusively used by the head position system, and cannot be used for storage of general data. The area of the disk surface allotted for embedded sector servo position information is thus overhead with respect to disk storage area. As disk capacity and TPI (track per inch) of current disk technology increase, the total number of sector servo position information fields on the track necessary to meet performance and shock vibration requirements also increases.
FIG. 1
illustrates a typical disk drive assembly
100
including spindle
104
, disk platter surface
102
, actuator arm
114
, head carrier
110
, servo positioning motor
116
, counter balance arm
118
, servo controller
120
and servo control circuit board
122
. The disk platter surface
102
may be coated with a ferro-magnetic material suitable for storing magnetic information. The mechanical layout of actuator arm
114
including a read and write head, as related to disk platter
102
and the disk drive chassis, is described in U.S. Pat. No. 6,049,440, which is hereby incorporated by reference in its entirety for all purposes.
FIG. 2A
illustrates conventional embedded sector servo position fields
200
inserted between data fields
250
of a track on a disk of a conventional disk drive assembly. The conventional sector servo position information fields
200
generally include a servo preamble, a servo address mark, a servo gray code and index, and servo bursts A, B, C and D, as illustrated in greater detail in FIG.
2
B. However, as disk capacity and TPI for disks of the conventional head drive assemblies have increased, compensation for spindle repetitive run-out (RRO) has become necessary.
As additional background, a servo preamble is a field typically used by a servo circuit in the data channel ASIC chip for servo circuit AGC (automatic gain control) and servo bit signal phase synchronization. During this field, the servo circuits establish proper signal amplitude and correct phase alignment for the servo address mark and following servo gray code and index field decoding. The servo address mark is a unique pattern field occurring after the servo preamble. The pattern is typically selected as a pattern having the least possibility of detection as actual data over the entirety of the track including the data field. Once the pattern is detected, a correct location on the track such as a mark on the disk can be used as a reference. This pattern field establishes the basic timing reference for the servo gray code and index field, as well as the reference timing for the burst field. The servo gray code and index field contains the servo track address, and may also include the servo sector address number and head number. Gray code encoding is typically used so that only one address bit changes from one track address to the next track address. The index typically is the first servo sector address number to indicate the beginning of a track. A servo sector address number (corresponding to the sequences of the servo sector field) may reach a few hundred. The servo burst field includes several burst fields for generating a position signal. A 4-burst scheme is widely used. A 6-burst scheme may be used to provide better linearity for the position signal, with an additional 2-burst overhead however.
FIG. 3A
illustrates a conventional track layout for a disk of a hard drive assembly, the track layout including embedded sector servo fields
300
inserted between data fields
350
. In this conventional track layout, a respective RRO field
303
is included for each sector servo field
300
. RRO field
303
is servo correction information that is used to compensate RRO during track following. In the track layout as illustrated in
FIG. 3A
, each RRO field
303
is used to compensate RRO during both reading and writing of the data fields, under the condition that offset between the MR head write element and read element on the head carrier is minimal. Additionally, a track servo parameter preamble and a track servo parameter sync mark, indicated as field
302
, is appended to each RRO field
303
, to enable the RRO field to be read.
In general, RRO fields
303
typically contain an RRO value and a few information control bits such as a defect bit, or other information bits to indicate the condition of the data field or the servo field itself (like bad, poor or good, for example). The RRO value is the compensation value for track following. Fields
302
and
303
are written onto the disk during manufacturing of the disk drive assembly. After several rounds of reading a position signal derived from a 4-burst or a 6-burst field, the analysis of these position signals provides information about spindle motor run-out. The badly written burst fields and/or defects can also be identified. The RRO value is the cancellation value that compensates the spindle motor repetitive run-out to allow the head to stay on the track, to prevent the MR head from wandering away from the desired track.
FIG. 3B
illustrates a conventional track layout including embedded sector servo fields
300
inserted between data fields
350
, that is similar to the conventional track layout of FIG.
3
A. However, separate write and read RRO fields
308
and
309
are respectively provided for each sector servo position field
300
. Each of the write RRO fields
308
include a corresponding write track servo parameter preamble and write track servo sync mark field
302
, and each of the read RRO fields
309
include a corresponding read track servo parameter preamble and read track servo sync mark field
302
. By using separate write RRO fields and read RRO fields, better track registration and performance may be achieved in a case wherein large offset is present between the MR head write element and read element on the head carrier.
The above described embedded sector servo fields including the servo correction information are inserted on the disk surface in pie-shaped sectors by the disk drive assembly manufacturer, as illustrated in FIG.
4
. The various tracks
1000
,
1001
and
1002
are divided into sectors
1003
,
1004
and
1005
for example, wherein embedded sector servo information fields
1006
including the servo correction information as described above are inserted on every track at a corresponding sector boundary. Conventionally, the sector servo information fields are each the same size and are equally spaced on the disk surface. The embedded sector servo area overhead of the disk surface is the ratio of the area used for head position servo fields to the area used for data storage. As may be particularly understood in view of
FIG. 4
, embedded sector servo area overhead of a typical disk is high. Thus, the disk surface area that may be used for data storage is limited, and this becomes especially noticeable as disk capacity and TPI rate of current disk technology increase.
SUMMARY OF THE INVENTION
The present invention is therefore directed to a method of interleaving servo information fields onto a track of a recording medium, and a rec
Aiello Jeffrey P.
Figueroa Natasha
Samsung Electronics Co,. Ltd.
Volentine & Francos, PLLC
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