A Compact Planar Quad-Channel SIW Filtering Crossover with Flexibly Allocated Channel Frequencies and Bandwidths

This paper presents a compact planar quad-channel substrate integrated waveguide (SIW) filtering crossover (FCR) with flexibly allocated center frequencies (CFs) and bandwidths (BWs) for all the channels. Four distinct substrate integrated rectangular cavities (SIRCs) operating with the orthogonal dual modes of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{TE}_{102}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{TE}_{201}$</tex> are designed specifically, cascaded adjacently, and coupled accordingly to allow a desirable transmission and inter-channel isolation performance, while enabling a flexible allocation of the channel CFs with a maximum frequency ratio of 1.32. By meticulously managing the resonant frequencies and mutual couplings among the constituent cavities, a flexible allocation of CFs and BWs can be achieved for each channel. Finally, a quadchannel SIW FCR with four channels centered at 26, 28, 30, and 32 GHz with the same BWs of 0.48 GHz is synthesized, designed, fabricated, and tested to demonstrate the feasibility of the proposed design scheme.