State space approach to design of continuous time sigma delta ADC with delay in feedback path

Excess loop delay is one of the major factors limiting the performance of continuous time sigma delta modulator (CTM). A solution is to provide an additional feedback path just before quantizer to compensate for this delay. Modified z- transform has been previously used as a technique to design the CTM incorporating the delay. In this paper we extend the work in (R. Schreier and B. Zhang, 1996) and present a state space based method to design such modulators. State space approach is preferred since it helps to automate the calculation of co-efficient using MATLAB. For the modulators with resonators in the loop filter, it is shown that using some results from z-transform techniques greatly simplify the design procedure.