Behavioural characteristics of ΣΔ modulators in time and frequency domains

The paper deals with the classification method of the behavioural characteristics of some architectures of Sigma–Delta (ΣΔ) modulators. The proposed method operates by analysing the different trends of the output signals characterizing the ΣΔ modulator architectures in the time or in the frequency domain once the input is the sinusoidal signal. The analysis in the frequency domain permits to distinguish between low pass and band pass ΣΔ modulator, and to classify the architecture as single quantizer loop (SQL) or multistage noise shapers (MASH). The analysis in the time domain permits to evaluate the number of levels of the quantizer block inside the SQL architecture and to detect the number of cascaded stages inside the MASH architecture. In order to validate the proposed classification method, numerical tests are performed by referring to the behavioural characteristics of numerous architectures proposed in the relevant literature.