On low-sensitivity realizations of band-elimination active filters

The results of an empirical search for low-sensitivity bandelimination active filters are presented. The search was oriented toward coupled topologies (leapfrog, coupled biquad, shifted companion form) and realizations that simulate passive structures (FDNR), as opposed to a solution by optimization. An 8th-order band-elimination filter was used as an example. A comparison between the above-mentioned realizations and the cascade shows that those topologies, while improving the sensitivity with respect to the cascade in some frequency bands, offer little or no improvement (if not impairment) in the other frequency bands. A sensitivity improvement over the cascade at all frequencies was obtained with a mixed topology, one which uses a cascade of properly chosen coupled sections.