Nonlinear effects in high-density tape recording

Nonlinearities in high-density tape recording have been studied. Dibit responses were measured versus recording density and write current. The dibit responses were then compared to the linear superposition of isolated transitions. It is shown that nonlinear bit shift and transition width changes are required to explain the differences. These nonlinear effects can be parameterized for signal processing purposes using the pulse response by including a timing shift and a time scaling for the second pulse response in a dibit. These parameters explain the observed difference between square-wave spectral response and isolated pulse FFT. A simple technique for obtaining head efficiency, the effective head-medium spacing, and the depth of recording is presented.