On the Implicit Anti-Aliasing Feature of Continuous-Time Multistage Noise-Shaping Sigma-Delta Modulators

This paper deals with one of the most outstanding advantages of continuous-time sigma-delta modulators compared to their discrete-time counterparts: the implicit antialiasing feature. Although inherent in any continuous-time architecture, calculation methods and discussions have mostly dealt with single-stage modulators in the past. This contribution covers the calculation method and the discussion of the antialiasing feature of continuous-time multi-stage noise-shaping sigma-delta architectures. A theoretical model will be introduced and confirmed through simulation results. Thereby, it will be proven that usually all stages of a cascaded architecture are involved in the anti-aliasing behavior and hence that it is not solely determined by the first stage.