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Track Pitch Independent Servo Pattern

IP.com Disclosure Number: IPCOM000099646D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 95K

Publishing Venue

IBM

Related People

Nakamura, T: AUTHOR [+2]

Abstract

A servo pattern as a reference of head position in a disk file device is described which is advantageous to be written and decoded accurately and economically. The width of servo pattern is set independent of that of data track. It is typically the same as the recording head width. The head position is detected once according to the servo track pitch. Then, it is converted to a track-dependent position by a simple conversion routine in the microprocessor on the file electric circuit.

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Track Pitch Independent Servo Pattern

       A servo pattern as a reference of head position in a disk
file device is described which is advantageous to be written and
decoded accurately and economically.  The width of servo pattern is
set independent of that of data track.  It is typically the same as
the recording head width.  The head position is detected once
according to the servo track pitch.  Then, it is converted to a
track-dependent position by a simple conversion routine in the
microprocessor on the file electric circuit.

      In recent disk file devices, servo control method is used as a
head positioner.  The controller references the servo pattern which
is written on the disk.  Therefore, the pattern must be accurate
since the writing cost is usually very expensive.

      Conventionally, the servo track pitch is just set to be equal
to that of the data track, as shown in Fig. 1. However, the head
width is shorter than that of the data track.  Then, the servo
pattern is written by an external head which has the same width as
the data track, as shown in Fig. 2.  Or, duplicated writing with
offset adjustment is done by the file's own data head.  The external
head method is accurate but not efficient. And the data head method
is not accurate enough because it is very hard to get fine writing
timing without a jitter problem, as shown in Fig. 3. In another prior
technology shown in Fig.  4, one servo pattern is written by a
duplicated writing operation by the data read/write head itself with
position offset.

      In this method, a cell of the servo pattern is configured in
the ma...