Abstract: Automatically optimizing and programming features of a disk drive read channel for a selected partial response (PR) target. This enables flexible PR targets to be used in the read channel. The flexible PR targets can have arbitrary coefficients, and the channel features (parameters, functions and algorithms) that are dependent on the flexible PR targets are automatically adapted and programmed in hardware or firmware. With flexible PR targets, the read channel can support longitudinal and perpendicular recording without compromising performance.

Abstract: A media noise optimized (MNO) detector for a read channel compensates for pattern dependent media noise, and compensates for nonlinearities from many sources such as residual MR nonlinearity, residual nonlinear transition shift, partial erasure, write-induced nonlinearity, and steady-state mis-equalization. The MNO detector is implemented by adjusting a conventional Viterbi detector branch metric so that the channel output value (ideal value) can be a nonlinear function of the state/branch bits, and the branch metric scaling factor is a function of the state/branch. For a given state/branch, the ideal value is the mean of analog-to-digital converter samples for the pattern corresponding to the state/branch, and the branch metric scaling factor is proportional to the noise variance for the pattern corresponding to that state/branch.