FIR filter design using highly non-linear LADF sigma-delta modulator architecture

In this paper we investigate the performance of multiplier free FIR filter design using an extremely non-linear Σ-∆ architecture. This architecture which is known as the Look Ahead Decision Feedback (LADF) circuit [1], has not been used in FIR filter design earlier. The circuit is highly non-linear because of the thresholding operation in the architecture. In this paper, we compare the LADF architecture with other conventional Σ-∆ architectures in the design of FIR filters. The noise characteristics of these architectures are discussed. It will be shown that the LADF architecture has relatively low noise power at low frequencies in comparison to other modulators. The design of optimum lowpass filters and comb filters for good noise reduction for LADF architecture is also addressed in the paper. Using a lowpass FIR filter design example, the appropriate filter design methodology is presented in the paper.