The Modeling Design of High-precision Sigma-Delta Modulator

Based on the MATLAB Simulink, the design of high-precision Sigma-Delta Modulator with single-loop third-order one-bit structure of CIFF is realized. The noise transfer function and feedback coefficients are optimized to enhance the stability of the system; and the main non-ideal factors in switch capacitor circuit are analyzed to provide a reliable guidance for transistor level circuit design. The simulation results show that when the signal bandwidth is 75 Hz and the sampling rate is 512, the SNR is as high as 148.3 dB; the ENOB is 24.34 bit and become 22.02 bit in the condition of various non-ideal factors, and become 20.94 bit when the designed modulator is realized by the real circuit. The results show that this structure can achieve high accuracy under low signal bandwidth.