NONLINEARITY MEASUREMENTS AND WRITE PRECOMPENSATION STUDIES FOR A PRML RECORDING CHANNEL

A general overview of nonlinearity measurement techniques is presented. For each technique, its accuracy, flexibility, and efficiency are studied analytically, assuming a recording system having only nonlinear transition shift and partial erasure. To distinguish partial erasure from nonlinear transition shift, a new frequency domain method is proposed. The test method was applied to study write current optimization, semi-contact recording and MR playback. Finally, a correlation factor, that relates the nonlinear measurement result to the optimal write precompensation level, is given based upon spinstand experiments. This correlation factor is then verified quantitatively utilizing an analytical model which includes only nonlinear transition shift.