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Servo Skipped Low Pole Switch

IP.com Disclosure Number: IPCOM000117998D
Original Publication Date: 1996-Aug-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Kurachi, K: AUTHOR [+4]

Abstract

To have robustness against Thermal Asperity (TA), it is effective to change the Low corner of the data frequency band (Low Pole) to the higher side. With this change, the Direct Current (DC) component of the TA signal settles faster, and the damaged length of the data can be minimized.

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Servo Skipped Low Pole Switch

      To have robustness against Thermal Asperity (TA), it is
effective to change the Low corner of the data frequency band (Low
Pole) to the higher side.  With this change, the Direct Current (DC)
component of the TA signal settles faster, and the damaged length of
the data can be minimized.

      Here is the problem.  The data band of the servo data is
usually much lower than that of the data area.  Then low pole
frequency for the servo data cannot be as high as that of the data
area.  Because if low pole frequency is close enough to the frequency
band, it brings signal distortion.

      One of the solutions to this tradeoff is to change the low pole
frequency for the data area and servo area.  Two different low poles
are provided.

      The last problem to be solved is the recovery of the channel at
the boundary of the data area and servo area.  Because at the
boundary, frequency band is changed, the channel needs some amount of
recovery time.  In order to handle this settling problem, the servo
skip technique  is introduced.  In the normal operation, read/write
is done using the servo pattern right before the target sector.  On
the other hand, in the  "Servo Skip", the servo right before the
sector is not used (skipped),  and the previous servo pattern is
used.  With this, the read/write operation is done much after the
channel recovery is completed, and the  settling problem is solved.