Designing CT bandpass ΣΔ modulators with arbitrary STF shapes

In this paper the automated design of continuous-time bandpass ΣΔ modulators with arbitrary signal-transfer-functions is described. State-of-the-art design methodologies rely on multiple transformations to obtain continuous-time bandpass modulators. Moreover, they are mainly focused on the NTF in order to achieve the required SNR. A design approach, which allows to realize a specified signal-transfer function is not known in the state-of-the-art. In contrast to that the web-based design tool www.sigma-delta.de allows STF engineering for bandpass modulators as first of its kind. The STF is optimized with regard to user defined specifications while the signal-to-noise ratio of the modulator is maximized. This work gives a general introduction to the tool and explains the features concerning bandpass modulators in detail together with corresponding examples.