Performance of maximum likelihood detectors in partial erasure

Partial Erasure is a well known phenomenon whereby closely spaced magnetic transitions in digital saturation recording partially erase each other. The resulting playback signals exhibit nonlinear pattern dependent amplitude losses. This paper defines and analyzes the performance of sequence detectors matched to a partial erasure model, matched to the RLL code d=0 or d=1 constraint, and also matched to the popular inter-symbol interference targets: PR4, EPR4, EEPR4, or EEEPR4. All of the d=0 detectors show losses on the order of -20*log/sub 10/(1-e) dB, where e is the fraction of the magnetic transition amplitudes erased in a di-bit. All of the d=1 detectors exhibit much less loss than the d=0 detectors. The d=1 EEPR4 and EEEPR4 detectors have no distance losses if e<0.2 and 0.37 respectively, even though significant signal energy is lost.