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Adaptive Symmetrical Interference Equalization

IP.com Disclosure Number: IPCOM000060467D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Schneider, RC: AUTHOR [+2]

Abstract

A technique is described for providing equalization to a magnetic recording signal. In the past, such equalization or pulse shaping was performed by a fixed equalization circuit. However, at higher recording densities, a single equalizer setting may not adequately compensate the signal across the total variation due to different heads, media and machines. An adaptive equalization loop is described hereinafter for providing equalization. The term "adaptive" is intended to cover compensation in random data without prior knowledge of what the data is, as opposed to other techniques which use "training sequences" or pulses of known data content to vary the amount of equalization.

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Adaptive Symmetrical Interference Equalization

A technique is described for providing equalization to a magnetic recording signal. In the past, such equalization or pulse shaping was performed by a fixed equalization circuit. However, at higher recording densities, a single equalizer setting may not adequately compensate the signal across the total variation due to different heads, media and machines. An adaptive equalization loop is described hereinafter for providing equalization. The term "adaptive" is intended to cover compensation in random data without prior knowledge of what the data is, as opposed to other techniques which use "training sequences" or pulses of known data content to vary the amount of equalization. The system described is based upon an assumption that the interference in the read pulse is symmetrical and that the read pulse is less than 4 bits wide. The interference is then detected, and a feedback signal is applied in the circuit to correct or equalize the interference. An assumption is made in that the read signal has passed through a fixed read equalizer (if necessary) such that the intersymbol interference is confined to, at most, one adjacent bit on either side. Since sampling is done at the center of data bit periods, the read pulse can be up to 4 data bits wide, as shown in Fig. 1. It is assumed that the amount of interference is approximately symmetrical. If J0, the system is under compensated, and if K00, the system is overcompens...