A model for overwrite modulation in longitudinal recording

An inherent contribution to overwrite modulation, a pattern of position shifts of the newly recorded flux transitions, is shown to result from magnetic fields from initial signal flux transitions superimposed on the head field during the overwrite process. A mathematical model was developed for this overwrite modulation mechanism for the case where a double frequency (2F) square wave signal is overwritten on a track initially recorded with a square wave signal of frequency F. The model predicted the qualitative form of the experimentally observed flux transition shift pattern, and was in quantitative agreement with measured overwrite modulation values for seven different magnetic recording tapes at two different recording densities.