Optimization of baseband incremental sigma-delta modulator based on stability and dynamic range

As the demand for sigma-delta (LA) analog-to-digital converters (ADCs) with higher bandwidth and higher signal-to-noise ratio (SNR) be increased, designers have to look for efficient structures with low oversampling ratio (OSR). However, decreasing the oversampling ratio would result in using the larger coefficients amounts in the modulator structure which jeopardize the modulator stability and its performance. In this paper, the total aspects of general order incremental sigma-delta (LA) modulators are analyzed. The operating principles of modulator and the main parameters like output dynamic range (DR), output effective number of bits (ENOB) and stability, in the time and frequency domain would be calculated and eventually the optimizing method based on an unconditional stability for modulator with maximum output dynamic range will be presented. All of derivations have been calculated for general order modulators. Simulation results in each section verify the trueness and precision of calculated parameters.