Mash modulator ΣΔ with highly reduced in-band quantisation noise

A novel class of multi-stage noise-shaping ΣΔ modulators is presented. The proposed structure achieves a one-order higher noise-shaping than the modulator´s order only by using two extra analogue paths. The noise transfer function zero optimisation is achieved by adjusting a single coefficient in the proposed modulator. Hence, with a minimal extra circuit, the signal-to-noise and distortion ratio is significantly increased compared with the conventional cascaded modulator. Analytical calculations and simulation results are provided to verify the usefulness of the proposed modulator.