Results on `controlled polarity´ modulation and coding

The authors present results on a controlled-polarity modulation/coding scheme. They review this scheme and describe how to choose certain code parameters for the purpose of comparing the controlled polarity scheme to conventional (d,k) coding with NRZI modulation. A computer simulation is then utilized to compare the different schemes in terms of effective signal-to-noise ratio (SNR) and peak shift. It is shown that the controlled polarity schemes have less peak shift than the conventional schemes, whereas the conventional schemes have a higher effective SNR. It appears that in systems with a high enough SNR, the loss in effective SNR could be outweighed by the decrease in average peak shift. This could be of particular interest in future systems using magnetoresistive heads which have the potential to yield substantially higher SNRs