Compact diplexer with dual-mode SIW resonators

A compact diplexer fabricated on substrate-integrated waveguide (SIW) technology is presented. The diplexer is a sixth order coupled-resonator network with no additional elements such as power dividers, composed exclusively of three dual-mode square SIW cavities. The coupling between the two orthogonal resonant modes of each cavity is generated by means of additional vias perturbing the cavity symmetry, while inductive irises implement the inter-cavity couplings. The coupling topology of the whole diplexer is restricted by the orientation of the resonant modes. A fabricated prototype with passbands around 10 GHz proves that this approach is feasible.