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Small Servo Signal Detection Method

IP.com Disclosure Number: IPCOM000114719D
Original Publication Date: 1995-Jan-01
Included in the Prior Art Database: 2005-Mar-29
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Murayama, M: AUTHOR [+4]

Abstract

Disclosed is a device for detecting smaller servo signal than normal signal. The servo signal is written inside of Hard Disk Drive (HDD). Normally servo signal are overwritten shifting by a half track. If the phase of each track signal is shifted by fluctuation of spindle rotation of HDD, the Servo signal will negate each other and become smaller (Fig. 1).

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Small Servo Signal Detection Method

      Disclosed is a device for detecting smaller servo signal than
normal signal.  The servo signal is written inside of Hard Disk Drive
(HDD).  Normally servo signal are overwritten shifting by a half
track.  If the phase of each track signal is shifted by fluctuation
of spindle rotation of HDD, the Servo signal will negate each other
and become smaller (Fig. 1).

      The technique for measuring a small servo signal is to sample
amplitude of servo signal (Fig. 2) and calculate Position Error
Signal (PES) for each sector with Analog Digital Converter (ADC).
The calculation formula of PES is as follows:
         PES = K / ( K + X )
         K :  constant value
         X :  sampling amplitude
  The amplitude of Servo Signal is inputed to ADC and the ADC
will calculate K / (K + X).  The output of ADC is represented by 8
bits (0 through 255).  If K is set to X,then output is 128,and X2 is
smaller than X1 (Fig. 3).

      This device can detect smaller servo signals of all the tracks
within a short time, by calculating standard deviation of PES for
each sector of a track and setting it as a criterion.