Dual Extended Noise Shaping for High Performance Cross-Coupled Sigma-Delta Modulators

A dual extended noise shaping based time-interleaved symmetric cross-coupled sigma-delta modulator, which enhances the performance of conventional unextended and extended noise shaping based time interleaved cross-coupled sigma-delta modulator architecture, is proposed in this paper. The N-path first order cross-coupled sigma-delta modulator can attain only Nth-order noise shaping for unextented case and (2N-1)th-order noise shaping in the extended case. By dual extended noise shaping characteristics, the proposed architecture can achieve 2Nth-order noise shaping out of an N-path cross-coupled first order sigma-delta modulator without sacrificing its high conversion rate and bandwidth. The higher order noise shaping is achieved by analytically obtaining the optimum coupling matrices. Compared to other alternatives, the dual extended noise shaping based time interleaved cross-coupled sigma-delta modulator exhibits a better in-band noise rejection with less overhead and relaxed circuit specifications.