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Seamless Servowriting for High-Track Density Magneto-Resistive Sector Servo System

IP.com Disclosure Number: IPCOM000115741D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Cheung, WL: AUTHOR [+4]

Abstract

Disclosed is a new way of servowriting the Position Error Signal (PES) pattern to eliminate the seam caused by the erase band in the PES bursts and also to minimize the seams in the sector ID. The resulting PES has a wider linear range compared with the PES patterns servowritten with seams. The PES burst is servowritten in one pass, and therefore there is no phase coherency requirement in servowriting the new PES pattern. Furthermore, by reducing the number of erase bands in the sector ID, the probability of failing to detect a sector mark or reading track address incorrectly is also reduced.

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Seamless Servowriting for High-Track Density Magneto-Resistive Sector
Servo System

      Disclosed is a new way of servowriting the Position Error
Signal (PES) pattern to eliminate the seam caused by the erase band
in the PES bursts and also to minimize the seams in the sector ID.
The resulting PES has a wider linear range compared with the PES
patterns servowritten with seams.  The PES burst is servowritten in
one pass, and therefore there is no phase coherency requirement in
servowriting the new PES pattern.  Furthermore, by reducing the
number
of erase bands in the sector ID, the probability of failing to detect
a sector mark or reading track address incorrectly is also reduced.

      In the prior art, each burst in the quad burst PES pattern is
one data track wide and is written in two passes during servowriting
with the head stepped at 1/2 of the track pitch.  The resulting burst
has a seam at the center due to the erase band arising from the
fringing field of the write head.  In addition, it becomes more
difficult to align the phase of the two half width bursts as the PES
burst frequency is increased to take advantage of the improved
resolution of advanced Magneto-Resistive (MR) read heads.
                                 PES   PES   PES   PES
                     SID          A     B     C     D
  Pass   N        SM   TA(m)      x    T2    T1    T2
  Pass (N+1)       x   x         T2    T1     x    T2
  Pass (N+2)      SM   TA(m+1)   T2     x    T2   ...