Performance tuning of multi-bit continuous time ΣΔ-modulators using a switched system model

This paper presents an approach to analyze and tune the dynamics of multi-bit continuous time ΣΔ modulators based on a switched system model. The illustrated model is used to calculate the input signal interval for each quantizer step and to change the system dynamics in order to adjust the input range between each quantizer level. With this method, it is possible tune the maximum stable input amplitude and the maximum signal to noise ratio to an optimum directly in continuous time. For that purpose, a linear scaling of the system dynamics is done. This yields to a scaling of each filter coefficient with a different factor, unlike the common method of simple scaling the loop gain of the system with a single linear factor. The presented method is demonstrated on a third-order modulator.