Media design considerations for a PRML channel

The requirements placed on the recording media by the partial-response maximum-likelihood (PRML) detection channel are examined in order to obtain optimum readback performance. It is noted that the use of a partial response (PR) data channel leads to somewhat different requirements for the recording media than are found for a conventional peak detector channel. The high transition density of current PR codes changes both the nonlinear behavior and the noise level in thin film media. Consequences of the different equalization techniques and sensor types have been explored. A by-product of the amplitude-sampling PR channel is a range of useful recording test functions which can be built into the channel and which can be used in a self-diagnostic mode