Constrained equalizer design for MDFE detection on the magnetic recording channel

Multi-level decision feedback equalization scheme (MDFE) is an excellent detection technique for magnetic recording channels using RLL(1, k) codes. In MDFE, the optimum equalizer is designed by maximizing the effective eye-opening divided by noise plus intersymbol interference. We address the problem of incorporating certain constraints in the equalizer design for achieving hardware simplicity and reduction in error propagation. In particular, we show that this constrained design results in (i) a critical loop clock-rate that is only 3/4 of the user data rate, (ii) a highly simplified feedback equalizer, and (iii) a mechanism to control error propagation. The results (theoretical and simulations) show that the performance degradation incurred due to these constraints is minimal.