Read channel issues in perpendicular magnetic recording

Perpendicular recording is an alternative to longitudinal recording that sh ows promise in mitigating the super-paramagnetic limit. This channel passes DC and thus presents challenges to the read channel design. Compounding th e problem, the MR head signal is susceptible to thermal asperities which ma nifest as low-frequency disturbances. We compare the performance of a DC-co upled PRML channel architecture which uses a non-DC-free target with a firs t-order DC loop to remove low-frequency disturbances to that of an alternat e architecture that uses a DC-free target. We show through analysis and sim ulation results that the former architecture degrades with increasing laten cy of the DC loop and performs worse than the DC-free target for large late ncies. In addition, the detection performance with DC-free target can be im proved by the use of a block code with single parity bit.