Miniaturized Dual-Band Filter Using Dual-Capacitively Loaded SIW Cavities

A dual-band filter using dual-capacitively loaded substrate integrated waveguide (SIW) cavities is proposed. Two conductive posts are embedded in the SIW cavity and the capacitive effect generated by the loaded posts lowers the first two resonant frequencies. Compared with the unloaded SIW cavity of the same size, the first resonant frequency is lowered by 39% (from 4.12 to 2.51 GHz), and the second resonant frequency is lowered by 20% (from 6.63 to 5.30 GHz). The two loaded posts also have the capability to tune the two resonant frequencies independently, thus two passbands of the filter using the loaded SIW cavity can be flexibly controlled. The proposed filter is fabricated through a multilayer printed circuit board (PCB) process to experimentally validate the predicted behavior.