An efficient design method for the modulator of high-order ΣΔ ADCs

Abstract

An exquisite high-order sigma delta (/spl Sigma//spl Delta/) modulator for specific application is hard to be achieved by a less experienced designer formerly. Now, a novel and efficient design method for high-order lowpass and bandpass /spl Sigma//spl Delta/ modulators is proposed. To begin with, the noise transfer function (NTF) of a /spl Sigma//spl Delta/ modulator is chosen from the transfer functions of the conventional analog filters. Rigorous stability constraints are employed to examine the NTF. Modulator parameters including oversampling ratio (OSR), number of the modulator order, and loop gain of the NTF are determined by system specifications. Thus, a modulator which fits the specific application with most economic system design parameters and minimum in-band harmonic distortion will be easily achieved.