New equalizer targets for sampled magnetic recording systems

In high density magnetic recording, signals are often equalized to a partial response target of the form (1-D)(1+D)ⁿ and then detected by a Viterbi detector using Euclidean distance. The authors use the ideas presented by L.C. Barbosa (1989) to estimate the performance degradation of several different equalizer targets for a tape channel, for a thin film disk channel, and for an ideal Lorentzian channel at a range of densities. The target 1+0.25D-0.75D ²-0.5D³ is shown to outperform the EPR4 target over a large range of densities. It is shown that in the absence of coding there exists little opportunity for performance improvements beyond those found with this target