Nonlinear Transition Shift and Write Precompensation in Perpendicular Magnetic Recording

The read-write process in perpendicular magnetic recording channels includes a number of nonlinear effects. Nonlinear transition shift (NLTS) arising from previously written transitions is one of these. The signal distortion induced by NLTS is reduced by use of write precompensation during data recording. In this paper, we numerically evaluate the effect of NLTS on the read-back signal by using the model proposed by Bertram and Nakamoto. By means of computer simulation, we examine the effectiveness of two write precompensation schemes in combating NLTS effects in a channel characterized by both transition jitter noise and additive white Gaussian electronics noise. We numerically optimize the precompensation schemes according to channel bit-error-rate, as well as more computationally tractable criteria. Our results suggest that a write-precompensation technique with as few as two adjustable parameters can be very effective against NLTS effects.