The Effect of Non-Linear MR Read-back Distortion on a PRML Channel

The effect of the nonlinear readback process of an MR head on a PRML digital magnetic recording channel was studied. Although the combination of a highly sensitive MR read head and a PRML channel is promising for high areal-density recording, nonlinearity in the MR readback process is a critical issue in the case of a channel in which linearity is assumed. We theoretically analyzed the characteristics of SHD (second harmonic distortion) as an index of the nonlinearity. Then, the effect of nonlinearity on the error rate was studied by computer simulation and in experiments. The results show that an SHD of less than -25 dB is required in order for the channel to be free of nonlinear distortion.