Theoretical and Experimental Evaluation of RZ and NRZ Recording Characteristics

Abstract

RZ and NRZ recorded pulse characteristics are determined theoretically and verified experimentally. Quantitative expressions are derived for the pulse location, width, shape and amplitude as a function of input current, head-tape spacing and gap width. The analysis is based upon the arctangent approximation for the head longitudinal field component and an empirical (also arctangent) expression for the tape magnetization curve. From the analysis, not only the effect, but the separate effects of field shape and magnetization curve on the pulse characteristics can be evaluated. It is shown that as the current increases, the pulse moves from the gap edge region towards the gap center line and then out again. The amount of pulse displacement, as a function of current, increases rapidly with larger head-to-tape spacing. The record drop-out sensitivity is directly related to the location of the pulse for NRZ peak sensing systems. At an optimum current level for different spacings, the location of the recorded pulse is found to be almost fixed; that is to say, the recorded dropout does not appear as a shift in pulse location but only as a drop in pulse amplitude. Since for small current and thus for small fields the remanent magnetization on the tape is approximately proportional to the applied field, the shape of the recorded magnetization, hence the recorded pulse, is given by the shape of the record head field.