Earticle

Sigma-delta ACD has two main parts: analog modulator and digital filter, the performance of modulator determines the performance of sigma-delta ADC, so the design of modulator is very important. The paper introduces the principle of sigma-delta AD modulator with high accuracy and the applied over sampling technique, noise shaping technique and multi-bit quantizer technique. Determining the design scheme of modulator—three bits three orders CIFF(Cascade of integrators, feed forward form) structure, and it makes the behavior level verification for this scheme by Simulink tool in MATLAB. The simulation result shows that multi-bit quantizer modulator can get very high SNR, and based on this result it designs every part of the modulator circuit.