Low Sensitivity, Low Power BP Active Filter Structures with Biquads using Impedance Tapering

This paper presents the realization of narrow high-order band-pass (BP) active resistance-capacitance (RC) filters. It was shown that such filters have large sensitivities to component tolerances, and if they were built using structures with multiple feedbacks, theirs sensitivities are substantially decreased. Furthermore, it was demonstrated that sensitivities of inner 2-order blocks (“biquads”) building the structure can be reduced by the “impedance tapering” design procedure. Using it we provide an additional decrease of BP filter structures sensitivities. As an illustration of the efficiency of the proposed design procedure, the sensitivity analysis, using Schoeffler’s sensitivity measure, is performed for an 8-order Chebyshev narrow BP filter. The filter was realised as: cascade (CAS), follow-the-leader-feedback (FLF), cascaded “biquarts” (CBQ) and leap-frog (LF) structure, using impedance tapered sub-circuits.