Reflectionless Filter Topologies Supporting Arbitrary Low-Pass Ladder Prototypes

Abstract

Modifications of the authors' previously published, generalized, lumped-element, reflectionless filter topologies are presented, which remove the original constraints on the relative values of its prototype parameters. Thus, any transfer function which can be realized as the transmission or reflection coefficient of a conventional ladder prototype may now be implemented in reflectionless form, i.e., having the same transfer function in transmission but with identically zero reflection coefficient at both ports and at all frequencies from dc to infinity, given ideal elements. The theoretical basis of these modifications is explained and then tested via the construction of passive, reflectionless low-pass filter prototypes that, in the prior topology, would have required negative reactive elements. The results show excellent agreement with theory.