Direct Bandpass Synthesis of Wideband Lumped-Elements Filters Using Inductive Couplings

This paper proposes an alternative way to represent and synthesize any filter network directly in the bandpass domain through the use of the coupling matrix and similarity transformations. For this purpose, a nodal representation is proposed that considers all elements of the filter network individually and independently of the fractional bandwidth. The proposed nodal representation allows the extraction of all lumped-elements directly from the coupling matrix. In this work, the direct bandpass synthesis of a wideband bandpass filter with inductive couplings, classically considered to be a 3rd-order filter in the lowpass prototype domain, is contemplated to validate the proposal.