Advanced read channels for magnetic disk drives

Advanced read channels which sample the read signal and process those samples using algorithms borrowed from the communications industry allow us to reach higher storage densities and faster data rates than ever before. In this paper we describe some of the design issues involved in using a PRML (partial-response, maximum-likelihood) channel in a disk drive employing thin-film heads, zoned-recording, and embedded servo sectors. We discuss the effect of high transition densities required for a PRML channel on the design of heads and media. Finally, we survey some additional signal processing methods which might lead to even higher performance in the future.<>