A methodology for designing continuous-time sigma-delta modulators

A methodology for analysis and synthesis of lowpass sigma-delta (ΣΔ) converters is presented in this paper. This method permits to synthesize ΣΔ modulators employing continuous-time filters from discrete-time topologies. The analysis method is based on the discretization of continuous-time model and using a discrete simulator which is more efficient than an analog simulator. Finally, a realistic design of a second-order ΣΔ modulator with a compensation of the non ideal behavior of DAC is given. Moreover, simulation results show a good agreement with the theoretical bases