Scale-modelling the read process for a film head

The read process has been studied in three dimensions for a film head by means of a large-scale model. It is shown that the readback voltage pulse can be obtained by simulating a magnetization impulse, using a narrow rectangular current loop with its plane perpendicular to the medium surface, and measuring the head flux generated by it. The on-track signal is compared with the sensitivity function for infinite head and track width, obtained analytically by Potter, et al [3]. It is found that the relative magnitude of the negative undershoot increases with decreasing head width as long as the head and track are about equally wide. By making the read head narrower than the written track, the pulse width is increased and the undershoot reduced. The off-track signal pulse is considerably wider than the on-track pulse, which explains why long wavelengths cause higher adjacent track noise than short ones.