Transition asymmetry in high density digital recording

The phase response of a tape-recording channel has been investigated from both theoretical and experimental aspects. A negative phase angle at short wavelengths corresponding to a playback pulse with the leading edge sharper than the trailing edge is usually observed in the experiment. This phase angle can be explained by asymmetric magnetic transitions in tape with a curved depth profile following the constant head field contour. Record current waveforms may alter the degree of transition asymmetry and change the phase response. Nonlinear distortion associated with the overshooting of record current waveforms has been found to be fairly insignificant. It is pointed out that tape interchange and compatibility in high-density digital recording require consideration of record head geometries, record current organization methods, and the shape of record current waveforms.>