Planar reflectionless filters

Abstract

The harmful effects that standing waves may have on an electronic system are well known. The symptoms of standing waves are less direct when they occur out-of-band, but the negative impact they have on system performance is no less real or important. Problems that arise from stop-band mismatches are in some ways even more troublesome than those in-band because they are too often not fully appreciated until after the first prototype is built, by which time some critical design and packaging decisions have already been made. Reflectionless filters provide a safeguard against these concerns. This chapter looks at reflectionless network topology, scaled prototype parameter tables, planar lumped-element implementations, delta-wye transformation for reduced impedance, non-canonical filter responses, transmission-line reflectionless filters, Chebyshev and Zolotarev type I filters.