An Elaborate Design and Implementation of a 3rd order Sigma-Delta Modulator ADC for Wideband Signals

The conventional sigma-delta (SigmaDelta) modulator structures used in telecommunication and audio applications usually cannot satisfy the requirements of signal processing applications for converting the wideband signals into digital samples accurately. In this paper, system design, analytical aspects and optimization methods of a third order incremental sigma-delta (SigmaDelta) modulator will be discussed and finally the designed modulator will be implemented by switched-capacitor circuits. The design of anti-aliasing filter has been integrated inside of modulator signal transfer function. It has been shown that the implemented 3rd order sigma-delta (SigmaDelta) modulator can be designed for the maximum SNR of 54 dB for minimum over- sampling ratio of 16. The modulator operating principles and its analysis in frequency domain and the topologies for its optimizing have been discussed elaborately. Simulation results on implemented modulator validate the system design and its main parameters such as stability and output dynamic range.