Browse Prior Art Database

Offset STW pattern

IP.com Disclosure Number: IPCOM000013736D
Original Publication Date: 2000-Mar-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 2 page(s) / 258K

Publishing Venue

IBM

Abstract

Disclosed is to measure read to write offset by Servo Track Writer(STW) and embed that into servo pattern. Read to write offset which is the difference radius position between read and write elements of MR head is varied for head to head as well as radius location. Therefore it should be measured individually before performing read/write the data. And it should be stored as micro-jog value in the Hard Disk Drive (HDD) system. Fig-1 shows the typical amplitude burst which is one of the part of servo pattern and radius position information for HDD servo controller. By assuming the position where the reading amplitude of burst A is equal to the one of B is track center. (express as (A-B)/(A+B)=0 While reading, read head is located on the track center. Though while writing, read head should be moved somewhere so that write head is on the track center ,ie (A-B)/(A+B) 0.3.

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Offset STW pattern

Disclosed is to measure read to write offset by Servo Track Writer(STW) and
embed that into servo pattern.

Read to write offset which is the difference radius position between read and
write elements of MR head is varied for head to head as well as radius location.
Therefore it should be measured individually before performing read/write the data.
And it should be stored as micro-jog value in the Hard Disk Drive (HDD) system.
Fig-1 shows the typical amplitude burst which is one of the part of servo pattern
and radius position information for HDD servo controller.

By assuming the position where the reading amplitude of burst A is equal to the
one of B is track center. (express as (A-B)/(A+B)=0 )

While reading, read head is located on the track center.
Though while writing, read head should be moved somewhere so that write head
is on the track center ,ie (A-B)/(A+B) = 0.3.

This read head location is defined as micro-jog.

Currently read to write offset measurement is done by observing read error rate
at manufacturing tester.

However this method takes long cycle time and has error ; measurement error itself
and rounded by certain dimension of polynomial expression.

By using STW read/write function and accurate positioning system, read to write
offset could be measured by positioning system counter unit,thus head could be
moved to reasonable location of its offset by positioning system.

Writing additional burst E and F shown in fig-2 which is located shifted by...