A novel noise-coupled time-interleaved delta-sigma modulator with analysis of practical limitations

TLDR: A new structure based on the Noise Coupled time-interleaved delta-sigma modulator is proposed to increase the overall noise transfer function order without any additional active element.

Abstract: An analog-to-digital converter based on the time-interleaved delta-sigma modulator is a proper method for high-speed ADCs. Time-interleaved delta-sigma modulators (TIDSM) can be successfully implemented with the development of the block digital filtering (BDF) technique. In this method, M mutually cross-connection delta-sigma modulators are used, with each one operating at a sampling rate of $${\text{f}}_{\text{s}}$$ hence, the effective sampling rate will be $${\text{M}}*{\text{f}}_{\text{s}}$$ However, SNDR is approximately equal to the single path standard structure. In this paper, a new structure based on the Noise Coupled time-interleaved delta-sigma modulator is proposed to increase the overall noise transfer function order without any additional active element. This improvement is analytically verified and then validated using simulations. Also, some practical issues regarding the implementation of the proposed structure, such as, finite op-amp’s gain and mismatching effects are discussed. Also, analyzes and some practical solutions are presented. The results of the simulation at the system level show that the SNDR of the proposed first-order two-channel structure is 18 dB better than its BDF technique counterpart, for the second-order two-channel TIDSM, the SNDR of the proposed structure is 13 dB better than that of the BDF technique.