Coding and Signal Processing for a Magneto-optic Resonant Bias Coil Overwrite Experiment

The resonant bias coil technique requires even-numbered transitions to be written on even-numbered clock cycles, and odd-numbered transitions on odd-numbered clock cycles. This constraint is met by double-spaced run-length-limited (d, k, 2) codes where the number of consecutive zeros is even. Exploiting the polarity of the transitions, a detection window that has double the size of the code bit period is possible. The authors describe a detection circuit that achieves the enlarged detection window, and present a phase detector which is particularly simple to implement. Channel bit-error-rate measurements have been carried out employing a rate 1/3 (2, 8, 2) code. Error rates of 10/sup -8/ were achieved for recording densities up to 33 kb/in. The results demonstrate the expected excellent immunity of the direct overwrite scheme to bloom.