Application to Digital Magnetic Recording

Abstract

In the last chapter, the performance of the proposed FDTS algorithm was analyzed on partial response channels corrupted by additive white noise. A partial response (PR) channel arises when the unconditioned channel spectrum matches with the assumed PR spectrum. PR channels possess many desirable characteristics [34]. When the channel match is poor, a linear equalization can be performed to shape the original spectrum into a given PR spectrum. When we have the freedom to perform linear equalization on the transmitter side, the pulse shaping can be achieved without enhancing the additive noise, which is usually presented on the receiver side. In high density magnetic recording, the unconditioned channel spectrum may not be sufficiently close to that of a PR channel. Also, because the head/medium interface of a magnetic recording system can only react to a step input, the PR equalization is performed at the read side. Thus, when a good spectrum match does not exist between the original channel and the target PR channel, performing linear equalization will always induce a large increase in read-side head/electronics noise. In short, forcing a recording channel into a pre-determined PR form may result in a significant performance loss.