A transversal equalizer with an increased adaptation speed and tracking capability

A modification to the well-known LMS (least-mean-square) algorithm for adaptive equalizers is presented. It allows a flexible tradeoff between throughput rate and adaptation speed by adjusting the arithmetic expense per output sample. If the arithmetic expense is increased to that of RLS (recursive least-squares) based algorithms a comparable adaptation speed is achieved. A full-custom implementation of a transversal equalizer using timesharing by a factor of two and Booth-coded coefficients proves the feasibility and efficiency of the modified LMS. It achieves data rates of up to 75 MBaud in a 0.8-μm CMOS technology under worst case conditions. The modification needs about 15% additional area in the basic cell of the filter, a few additional control signals and a buffer to store 40 input symbols