A DT 0–2 MASH ΣΔ modulator with VCO-based quantizer for enhanced linearity

This paper presents a new structure of the discrete time 0–2 MASH sigma-delta modulator implemented with VCO-based quantizer in the second stage. The proposed scheme enhances the linearity of the VCO based quantizer, meanwhile it takes advantage of the intrinsic DEM function and first order noise shaping in the second stage. Besides, the matching requirement is relaxed and the digital canceling filter is largely simplified. Moreover, no additional active adder in or between two stages is needed because of the 0–2 MASH structure, which can save a lot of power. The proposed DT 0–2 MASH sigma-delta (ΣΔ) modulator with 10MHz signal bandwidth for wideband applications is designed and simulated in Matlab. The performance of the modulator can reach 97dB SND Runder a sampling rate of 1.15GHz.