Pedestal substrate integrated waveguide filter with both electric and magnetic cross-couplings

Abstract

In this paper, the recently proposed Pedestal Substrate Integrated Waveguide (SIW) structure, consisting of evanescent-mode SIW cavities, loaded with pedestal-shaped metal inserts, is utilized to design a coupled resonator filter with both positive and negative cross-coupling. It is shown that both types of coupling, for a large range of coupling values for both, can very simply be implemented in this structure, with electric coupling obtained by means of an I-shaped strippine between pedestal tops, and magnetic coupling obtained using inductive irises. The proposed structure can also introduce mixed coupling. Graphs are presented to show the range of coupling values attainable. A proof-of-concept sixth order cross-coupled bandpass filter, with a 5 % bandwidth at 5 GHz, and both real and imaginary axis transmission zeros, are designed and measured.