Reflectionless Filter Topologies Supporting Arbitrary Ladder Prototypes

TL;DR

This paper introduces modified reflectionless filter topologies that can implement any ladder prototype transfer function with zero reflection at all frequencies, expanding design flexibility for passive filters.

Contribution

The authors present generalized reflectionless filter topologies that remove previous parameter constraints, enabling realization of any ladder prototype with zero reflection across all frequencies.

Findings

Successful construction of passive, reflectionless low-pass filters

Excellent agreement between theoretical predictions and experimental results

Ability to realize any ladder prototype with zero reflection

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 --- that is, 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.