Signal processing for single and dual element unshielded magnetoresistive heads

Single and dual element unshielded magnetoresistive (UMR and DMR) heads have potential for extremely high density magnetic recording, but saturation and unusual readback waveforms must be dealt with. Two new peak detector channels take advantage of the unusual waveforms: (1) The quasi-integrating channel for the UMR, whose output is similar to that of integrating channels with inductive read heads. Performance may be enhanced by adding short pulses to the write current at distances greater than T/sub min/ from code 1 transitions. (2) Controlled polarity recording with decision feedback, which is a special case of write equalization where successive pulses may have the same polarity. The detection window is twice that of conventional recording. Simulated performance is comparable to PRML channels.<
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