Compact decimation filter for constant-input oversampling Sigma-Delta Modulators

Abstract

This paper proposes a compact nonlinear algorithm, Approacher, to raise the resolution of the digital decimation filter at the post-stage of constant-input oversampling Sigma-Delta Modulators (SDMs). Because the proposed Approacher algorithm is evolved from the fundamental linear algorithm, Averager, the proposed Approacher algorithm is east-to-implement and high-efficiency. According to the numerical results from Mathematica, in the first-order SDM, it shows that SNR of the proposed Approacher decimation filter is 4.8 dB better than that of the fundamental Averager decimation filter. In the second-order SDM, it shows that SNR of the proposed Approacher decimation filter is 2.0 dB better than that of the fundamental Averager decimation filter. Besides, the proposed nonlinear decimation filter can be easily applicable to all current oversampling SDM structures, like first-order, second-order, cascaded, and interpolative SDMs.