A Hybrid RNS Adaptive Filter for Channel Equalization

In this work a hybrid residue number system (RNS) implementation of an adaptive FIR filter is presented. The used adaptation algorithm is the least mean squares (LMS). The filter has been designed to meet the constraints of specific class of applications. In fact, it is suitable for applications requiring a large number of taps where a serial updating of the filter coefficients is feasible (channel equalization or echo cancellation). In the literature, it has been shown that the RNS implementation of FIR filters grants earnings in area ad power consumption due to the introduced arithmetic simplifications. Vice versa, the RNS implementation of the adaptation algorithm needs scaling circuits that are complex and expensive in RNS arithmetic. For this reason, a serial binary implementation of the adaptation algorithm is chosen. The advantages in terms of area and speed of the RNS adaptive filter with respect to the two´s complement one have been evaluated for a standard cells implementation.