Design of hybrid continuous-time discrete-time delta-sigma modulators

Recent attention has been drawn to the hybrid Delta-Sigma (DeltaSigma) structure featuring the integration of continuous-time (CT) and discrete-time (DT) structures in the loop filter. It combines the accurate loop filter characteristic of a DT DeltaSigma modulator and the inherent anti-aliasing of a CT DeltaSigma modulator. We present a design methodology for building a CT-DT DeltaSigma modulator via the transformation from a DT DeltaSigma modulator prototype. We also demonstrate the tradeoff of applying this structure to cascaded Delta-Sigma modulators compared to pure CT or DT implementations.