New dual-quantization multibit sigma-delta modulators with digital noise-shaping

A new architecture of multibit Sigma-Delta modulator with dual-quantization is proposed here where the multibit DAC in the feedback path is replaced for a single-bit one. Unlike other dual-quantization architectures based on digital cancellation, the proposed one is based on an additional feedback path in the input of the second modulator composed of a quantizer with digital noise-shaping, a digital integrator and a multibit DAC. The non-idealities of the later are not critical because they are shaped by the transfer function of the first integrator. When compared to other dual-quantization architectures, the proposed one is more robust against mismatches between the analog and digital paths, at the cost of an increased complexity. Theoretical and simulation results are presented.