Modeling and simulation of digital recombination network for 2-1-1 cascaded doubled-sampled delta-sigma modulator

A mathematical model of the digital recombination network for 2-1-1 cascaded double-sampled (dS) delta-sigma (Delta Sigma) modulator, is presented. The model in the z-domain is used to evaluate the performance of the modulator, when the components mismatches are included. A 2-1-1 dS Delta Sigma modulator that operates from a single 2.5-V supply is designed in 0.6-mu m CMOS technology. The clock frequency is of 26.4 MHz, making the effective sampling of 52.8 MHz, which results in the required signal bandwidth for Asymmetrical Digital Subscriber Line (ADSL) applications of 1.1 MHz. The modulator is evaluated with the mathematical model using MATLAB, and for an oversampling of 24, the modulator achieves a signal-to-noise ratio (SNR) of 88-dB, a signal-to-(noise + distortion) ratio (SNDR) of 84-dB, and a dynamic range (DR) of 91-dB.