Compact wideband substrate integrated waveguide bandpass filter for X/Ku-band application

This article presents a novel design of a compact substrate integrated waveguide (SIW) wideband bandpass filter. The proposed bandpass filter offers wide passband, wide lower, and upper band rejection characteristics. First, the filtering response is obtained by loading a single T-shaped slot on the top of the SIW structure. Later, to achieve wide passband and wide upper band rejection, a pair of T-shaped slots has been engraved on the top surface. To demonstrate the analysis, the proposed SIW filter has been simulated, fabricated, and tested. The measured S-parameters are in good agreement with the simulated results, showing wide passband from 8.05 to 15.45 GHz within a 3-dB fractional bandwidth of 62% at a center frequency of 12 GHz. The measured return loss is fairly good (>17 dB) within the passband and an insertion loss of 0.5 dB, including the loss from two SMA connectors. The fabricated prototype has a compact size of 0.248 lambda(2)(g).