Performance of random-access-memory-based equalizers in magnetic recording

We discuss two algorithms for mitigating the deleterious effects Of nonline ar intersymbol interference in PR4-algorithms RAM-Search algorithms because they borrow the idea of employing random-access memory (RAM) from the RAM. decision-feedback equalizer-(DFE) and because they involve a search. The R AM-Search algorithms have been devised to mitigate the error propagation pr oblem that arises in making feedforward decisions (for precursor terms) in intersymbol interference (ISI) cancellers used in combination with partial- response signaling. We adopt a simple partial-erasure model for the:nonline ar write process and a third-order polynomial model for the nonlinear read process, and show that improvements of about 2.5 dB are possible. We also d emonstrate the efficacy of the algorithms on captured spinstand signals tha t suffer from a significant amount of nonlinear ISI.