Characterization and equalization of dropouts in the magnetic tape recording channel

Abstract

We consider the issue of combating signal dropouts in magnetic tape recording. Dropouts are a major limiting factor in the performance of the channel as they cause long bursts of bit errors. To attack this problem, a model of the dropout event has been developed. Based on that model, a strategy has been identified in which an envelope detector followed by a feedforward equalizer is used. The equalization process is done in such a way as to address the three major effects caused by a dropout event: amplitude loss, pulse widening and peakshift. The crucial part of this scheme is the spacing profile estimator, which makes use of an envelope detector. With this scheme, the effects of the dropout are corrected at the expense of a delay in the channel. The model of the dropout and the correction scheme are all presented.