Synthesis of IIR error feedback filters for ΔΣ modulators using approximation

摘要

In this paper, we propose a design procedure to obtain infinite impulse response (IIR) error feedback filters for ΔΣ modulators. It is known that the design of optimal finite impulse response (FIR) error feedback filters for ΔΣ modulators can be cast into a convex optimization problem, while the design of IIR error feedback filters cannot. To design IIR error feedback filters, we first obtain the optimal FIR error feedback filter and then approximate it with an IIR filter. As an example, we utilize the H∞ norm of the filter to design the optimal filter. We provide design examples to show the effectiveness of IIR error feedback filters for ΔΣ modulator designed by our proposed method.