A Compact Harmonic-Suppressed Filtenna Based on Miniaturized High-Order Half-Mode SIW Cavity

A compact harmonic-suppressed filtenna (filtering antenna) for multiantenna system applications is presented in this letter. It only consists of a miniaturized substrate integrated waveguide (SIW) half-TE120-mode cavity, a radiating patch, a row of metallic central vias, and a feeding probe. By using the shielded combined boundaries of electricity via walls and U-shaped slots, the SIW half-TE120-mode cavity can reduce its size by 76.3%. As the reduction of size and the addition of central vias, the proposed cavity exhibits good harmonic suppression. The central vias can also be employed to push the radiation null produced by the SIW cavity half-TE110 variant mode to the lower passband edge. Due to the cross coupling between radiators, a new radiation null can be introduced to synthesize the bandpass filtering response. Because there are neither external filtering circuits nor special parasitic filtering resonators, the structure of the proposed filtenna can be kept simple. A prototype centered at 5 GHz was fabricated and measured for demonstration, indicating an impedance bandwidth of 14.4%, a peak gain of 7 dBi, and a wide stopband of up to 10 GHz.