DR and SNR improvement for 3rd and 4th order ΔΣ modulators using genetic algorithm

In this paper, a new method to find gain coefficients of 3rd and 4th order Delta Sigma modulator aimed at increasing the dynamic range and relative improvement in SNR value is presented. The most restricted part in designing of Delta Sigma modulators is the design of noise transfer function to make shaping of quantization noise and then find the gain coefficients of the different structures by using the obtained noise transfer function. The structure is chosen for the simulations carried out in this paper is CIFB. For this purpose, the obtained gain coefficients by using genetic algorithm and the results are compared by Delsig toolbox. Simulations have been done with MATLAB and with completely identical in terms of maximum out-of-band NTF gain and the number of sampling points for fair in system level conclusions. Using proposed method, DR of 3rd and 4th order modulators can be improved till 4.1dB and 3.7dB for different OSRs, respectively.

Keywords:

sigma delta modulator , genetic algorithms , optimal filter design ,