An adaptive DFE for storage channels suffering from nonlinear ISI (magnetic recording)

The authors explore the magnetic recording channel in some detail and describe some of the characteristics of the channel that point to the random access memory decision feedback equalizer (RAM-DFE) as a suitable detection method. The structure and adaptation of the RAM-DFE are described. The RAM-DFE with the signed-LMS (least mean square) algorithm and the constrained step size ( mu =2/sup -n/) is shown to be well suited to the magnetic storage application. Not only does RAM-DFE outperform the conventional DFE under many circumstances, but it is also more conducive to a high-speed digital implementation, making the RAM-DFE appropriate for the higher data rates (linear densities) that its improved performance facilitates. Preliminary investigations indicate that the RAM-DFE can be implemented in 1.6- mu m CMOS on a single VLSI chip (about 50000 transistors) with a sampling (data) rate of 54 MHz.<
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