Read channels for prepatterned media with trench playback

Patterned media can be prepared by depositing conventional continuous-film media on prepatterned substrates, such as DVD-like plastic disks. Significant playback signals are produced from media deposited in the substrate trenches, at terabits-per-inch/sup 2/ lithographic feature size limits. Three recording channels are analyzed to deal with these signals - standard symmetric-pulse partial response maximum likelihood (ignoring the trench signal), an asymmetric partial response channel with different positive and negative pulse targets, and simple cancellation of the trench signal. The latter has the best bit-error rate (BER), even with 10% cancellation errors. Perpendicular media without an underlayer had superior BER to horizontal.