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Write Precompensation Method for Magnetic Recording Using Current Amplitude Or Rise-Time Modulation

IP.com Disclosure Number: IPCOM000121619D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 3 page(s) / 77K

Publishing Venue

IBM

Related People

Hoyt, RF: AUTHOR [+2]

Abstract

A write precompensation method using amplitude or rise-time modulation of the write-head current is described. Write Current Amplitude Modulation

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Write Precompensation Method for Magnetic Recording Using Current
Amplitude Or Rise-Time Modulation

      A write precompensation method using amplitude or
rise-time modulation of the write-head current is described.
Write Current Amplitude Modulation

      The write-current amplitude modulation technique can be used in
situations where the write head does not saturate. This allows some
freedom in controlling the size of the region around the write gap
which has field strength exceeding the coercivity of the disk.  We
call this region a write-bubble.  Additionally, we assume that the
relative speed between the head and the disk is slow compared to the
"growth" rate of the write-bubble.  Thus, the location of the
magnetic transition written on the disk is a linear function of the
size of the write-bubble.  By changing the write current, we then
achieve write- precompensation.  A simple write driver circuit
capable of quickly changing the write current is shown in Fig. 1.
The upper part of the write driver is a conventional write driver.
However, the current source for the driver is now a current switch
array. The current sources shown can be implemented using ratio
matching current mirrors.  Thus, the current switch array can be
easily integrated with the upper portion of the write driver into a
single chip.

      Non-ideal conditions may cause a certain amount of pulse shape
modulation as well as non-linearity in the amount of precompensation.
This is not a problem since the amount of precompensation can be
adjusted for optimum performance.
Write Current R...