Balanced bandpass filter with tunable centre frequency based on substrate integrated waveguide technology

A mechanical tuning balanced bandpass filter based on substrate integrated waveguide (SIW) dual-mode resonant cavity is presented. It can be accomplished by placing two metallised via-holes with open-loop slots on the top layer which affect the TE102 and TE201 modes of the square SIW cavity, respectively. Direct source-load couplings have been utilised to achieve the high selectivity of the differential mode (DM) passband and improve the DM out of band rejection. A planar module of 60 × 60 mm2 has been fabricated on RO5880 substrate with a dielectric constant of 2.2 which verify the design concept.