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Improved Dedicated Servo Pattern for Rigid Disk Magnetic Storage Systems

IP.com Disclosure Number: IPCOM000115705D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Arnoldussen, TC: AUTHOR [+4]

Abstract

An improved method of writing the quad-burst servo pattern was developed. The method results in "seamless" servo pattern transitions and generates greatly improved servo performance.

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Improved Dedicated Servo Pattern for Rigid Disk Magnetic Storage
Systems

      An improved method of writing the quad-burst servo pattern was
developed.  The method results in "seamless" servo pattern
transitions and generates greatly improved servo performance.

      Quad burst servo patterns are normally written by over writing
one-half or one-third of the transitions.  Because of the side
fringing of the head during the write process, the overwrite causes a
gap in the final transition.  This gap degrades servo performance by
increasing the non-linearity of the servo signal vs off track
position.

      A method of writing the servo pattern which completely removes
the transition gap was developed.  The normal write procedure is to
continuously pass current through the head.  The direction of current
is switched when a transition is desired.  This could be called a
two-state write process.  The new method is a three state process.
The third state is no current and this state is used when it is
desired to pass over an existing transition without an overwrite.
The write process is carefully synchronized with the quad burst
pattern and results in seamless transitions.

      This system was implemented on the servo writer for the 3390-3
product.  The test stand measurements indicated a non-linearity of

6.9% using the two state method, and less than 1% using the three
state method.