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Browse Prior Art Database

Magnetic Recording via Look-up Tables

IP.com Disclosure Number: IPCOM000104292D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 1 page(s) / 30K

Publishing Venue

IBM

Related People

Cocke, J: AUTHOR [+4]

Abstract

Disclosed is a method for magnetic recording of a class of constrained signals using look-up tables in a dynamic fashion.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 88% of the total text.

Magnetic Recording via Look-up Tables

      Disclosed is a method for magnetic recording of a class of
constrained signals using look-up tables in a dynamic fashion.

     The invention writes signals whose outputs by the read head are
of the form

           s(t) %% = %% sum from k % a sub k % f ( t - k T )
where a sub k % = % pm 1, f(t) is some prescribed fixed pulse shape,
and T is some fixed time interval.  Of main interest is when T is so
small that ideal transition cannot be achieved at such interpulse
intervals.  It is assumed that the channel memory is of duration less
than KT, where K is some integer.  This means that the the function
f(t) is identically 0 outside the interval ((k-K)T % , % (k+1+K)T).
Thus, in every time period of duration (2K+1)T, there are only 2 sup
<2K+1> possible signals in the read output.

     The present invention proposes to create a look-up table with 2
sup <2K+1> entries, each one being the write current necessary to
create one of the allowable signals in the output.  At a given time
interval (kT % , % (k+1)T), if the code for the interval ((k-K)T % ,
% (k+1+K)T) is the sequence a sub <k-K> % , % a sub <k-K+1> % , %
....  % , % a sub <k+1+K>, then the write current to be employed is
that portion of the signal in the lookup table, indexed by a sub
<k-K> % , % a sub <k-K+1> % , % ....  % , % a sub <k+1+K>, which is
in the interval (kT % , % (k+1)T).

     The present invention also proposes that the lookup tabl...