A thin-film head design technique to correct read pulse asymmetry

Abstract

The read characteristic pulse from a longitudinally oriented head/disk interface is asymmetric, and this can be viewed as phase distortion. One of the major causes is related to the record-demagnetizing process which is essentially non-symmetrical. A thin-film head design technique, capable of restoring the read pulse symmetry is conceived and simulated. By choosing different leading and trailing pole-piece thicknesses for compensation, it is possible to correct the phase distortion at the problem origin. For a 3370 type head/disk interface at 520 flux changes per millimeter, a 25% increase of the leading pole-piece thickness from that of a standard thin-film head can reduce worst cased (triplet pattern) amplitude variation from 8.5% to 1.3%. The corresponding peak shift is also marginally decreased. This thin-film head design technique is simple to implement and can eliminate the costly phase correction circuitry usually used for signal post processing.