Cascade 2–2 sigma-delta modulators for wideband high-resolution applications

In this paper, several techniques which relax circuit requirements of building blocks are presented to effectively realize wideband high-resolution cascade sigma-delta modulator. Three cascade structures have been proposed in this paper. First, a MASH 2-2 with feed-forward topology in both stages has been explained to obtain low-distortion property and remove subtraction Second, a flexible SMASH 2-2 has been proposed to choose appropriate coefficients for different requirements. Third, a SMASH 2-2 with feed-forward quantization noise self-coupled structure has been displayed to cancel quantization error of the preceding stage totally. Detailed simulation results and comparisons demonstrate the performance of these topologies.