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Space Efficient Position Error Burst Pattern and Demodulation

IP.com Disclosure Number: IPCOM000122791D
Original Publication Date: 1998-Jan-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 4 page(s) / 85K

Publishing Venue

IBM

Related People

Cheung, W: AUTHOR [+4]

Abstract

Head positioning control in a disk-drive is dependent on having a sufficient number of position error samples around a track. Embedded servo information provided by the servo pattern reduces the overall storage area for data. It is important to keep the length of the servo information pattern as short as possible within a sector format. In the prior art, servo burst pattern is segmented with spaces between servo bursts as shown in Fig. 1, a two-burst pattern, and in Fig. 2, a quad-burst pattern. The spaces within the sector servo pattern cause overheads for disk drive storage.

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Space Efficient Position Error Burst Pattern and Demodulation

      Head positioning control in a disk-drive is dependent on having
a sufficient number of position error samples around a track.
Embedded servo information provided by the servo pattern reduces the
overall storage area for data.  It is important to keep the length of
the servo  information pattern as short as possible within a sector
format.  In the prior art, servo burst pattern is segmented with
spaces between servo bursts as shown in Fig. 1, a two-burst pattern,
and in Fig. 2, a  quad-burst pattern.  The spaces within the sector
servo pattern cause overheads for disk drive storage.

      Disclosed is a new servo pattern and an associated digital
sampling and demodulation method for achieving space efficiency in a
disk drive sector servo system.  A servo burst of the pattern is
formatted with magnetic transitions which are phased 180 degrees from
opposite sides of the track center as shown in Fig. 3.  The new
pattern is efficiently formatted and has no spaces between the useful
servo bursts.  The servo bursts are placed next to a standard sector
servo AGC/Sync field burst, and included a normal servo burst and a
quadrature servo burst.  The AGC/Sync field is used as a reference
servo burst in this invention.  The normal servo burst transitions in
the upper track are spaced in -90 degrees shifted from the reference
burst, the normal servo burst transitions in the lower track are
phased + 90 degrees from the reference burst.  The normal servo burst
contains the servo position information.  The quadrature servo burst
provides additional servo position information for an extended linear
range.

      Demodulation of the pattern is accomplished with quadrature
digital sampling with produces two series of samples...