MEDIA SELECTION FOR HIGH-DENSITY RECORDING CHANNELS

The implementation of high density partial response channels in disk drives has been hampered by nonlinear interactions between transitions occurring in the write process. It is shown that the degree of nonlinearity is not characterized by the density relative to the isolated transition pulse width, rather by the transition spacing in relation to the transition width. Factors that determine the transition width are examined. In particular, the potential gains from using low moment media are investigated. A nonlinear model of the disk channel is discussed. The dependence of partial response signaling on linear superposition is discussed. Eye patterns are shown revealing the effects of nonlinearites on a partial response system.