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Write Precompensation for Peak Detection of Partial Response Signals

IP.com Disclosure Number: IPCOM000112017D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Melas, CM: AUTHOR

Abstract

Disclosed is a method for correcting interference between readback signal transitions which enables peak detection at greater densities. By modifying the position of existing flux transitions and inserting additional transitions, a partial response signal can be created with constant peak amplitude and no peak shift, thus increasing density from 25% to 33% without loss of resolution or additional equalization.

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Write Precompensation for Peak Detection of Partial Response Signals

      Disclosed is a method for correcting interference between
readback signal transitions which enables peak detection at greater
densities.  By modifying the position of existing flux transitions
and inserting additional transitions, a partial response signal can
be created with constant peak amplitude and no peak shift, thus
increasing density from 25% to 33% without loss of resolution or
additional equalization.

      The magnetic readback signal is composed of flux transition
responses, assumed to be symmetrical pulses.  At high densities,
interference between consecutive pulses occurs, and the readback
signal becomes a partial response signal.  Considering interference
from neighboring pulses only, the partial response signal may have
one of three different types of peaks: 1) isolated peaks having no
Inter Symbol Interference (ISI), of high amplitude and no peak shift;
2) peaks of medium amplitude with interference from a single
neighboring pulse, generating peak shift; and 3) peaks of small
amplitude with ISI from two neighboring pulses.  If one considers the
binary data as composed of blocks of n ones, separated by one or more
zeroes, the large peaks correspond to blocks having a length of one
clock cycle (isolated transitions), the medium peaks to the first and
last bits of blocks having a length greater than one clock cycle, and
the small peaks to the "inner bits" of these latter blocks.  There is
no ISI between blocks.

      The Partial Response (PR) signal is precompensated to achieve a
desirab...