Design of Dual/Tri-Band Filtering Antenna Using Multi-Mode SIW Cavities

Compact, vertically-integrated dual- and tri-band filtering antennas based on multi-mode substrate integrated waveguide (SIW) cavities are developed. The electric filed distributions of the resonant modes in a SIW cavity are firstly analyzed. And then, a dual-band SIW filtering antenna is developed by employing a dual-mode SIW cavity and a slot-loaded SIW cavity. In the dual-band design process, a SIW cavity, operating at its TE
110
and TE
120
modes, is utilized as the feeding cavity, and a slot-loaded SIW cavity is stacked over the dual-mode SIW feeding cavity to simultaneously realize the dual-band function and facilitate the filtering response for both two passbands. Finally, in order to achieve the tri-band function, a multi-mode SIW cavity, operating at its TE
110
, TE
120
, and TE
210
modes, is selected as the feeding cavity. According to properties of the electric field magnitude distributions of the three modes in SIW cavity, the position of the feeding line is elaborately designed to simultaneously excite these three modes. Likewise, a slot-loaded SIW cavity is employed to stack with the multi-mode SIW feeding cavity to accomplish the tri-band function and improve the frequency selectivity for three passbands. The simulated results demonstrate that both the dual-band and tri-band SIW filtering antennas possess good in-band and out-of-band performance characteristics.