Tuning of Passband in Compact Substrate Integrated Waveguide Bandpass Filter by Controlling Higher Order Modes

This paper presents a standard process for tuning the center frequency and bandwidth of a dual mode passband by controlling the higher order orthogonal modes of a compact substrate integrated waveguide (SIW) cavity. The bandpass filter is based on a cascaded dual cavity structure, derived from circular SIW and metallic vias are introduced to control the passband generating modes. Dimension and position of the tuning vias are varied to control the orthogonal modes and tune the center frequency of passband within a range of 8 GHz to 10 GHz. More than 3% change in resonance frequency and 3% change in bandwidth are shown in the simulated results with 1.62 dB minimum insertion loss and nearly 15 dB return loss in passband.