Switched-capacitor LDI lowpass filters with improved selectivity

Generalised expressions are given for transfer functions of an extensive family of lowpass switched-capacitor LDI ladder filters with optimum equiripple (or maximally flat) passbands and an arbitrary number of transmission zeros at half the sampling frequency. These allow greater flexibility in the design and permit tradeoffs to be made among factors such as sampling frequency, element value spread and dynamic range. The previously studied LDI filters with monotonic stopbands can be recovered as degenerate special cases of the generalised ones presented here.