Varactor-Loaded Tunable SIW Filter with Wide Upper Stopband Characteristic

In this paper, varactor-loaded tunable substrate integrated waveguide (SIW)-based filter is presented. Initially, a SIW cavity is designed at higher frequency range. The stepped-impedance low-pass filter slots are embedded as a slot on the top of the cavity structure in order to suppress the higher order modes of the SIW cavity. The passband is centered 5.25 GHz to pass the WLAN band with excellent selectivity. The stopband characteristic of the proposed filter is satisfactory due to absence of higher order modes. The proposed structure is EM-simulated to verify the theoretical analysis.