Wideband Triple- and Quad-Resonance Substrate Integrated Waveguide Cavity-Backed Slot Antennas With Shorting Vias

A triple-resonance and a quad-resonance substrate integrated waveguide (SIW) cavity-backed slot antennas using shorting vias are presented in this paper. The antennas have wide bandwidths and low profiles. The working mechanism of the triple-resonance antenna is explained with its electric field distributions and equivalent circuit models. By loading the SIW cavity with shorting vias, the lowest mode (half-TE110 mode) is shifted upward and coupled with two higher modes (even and odd TE210 modes). As a result, a wide bandwidth with triple resonances is achieved for the antenna. Based on the similar principle, a quad-resonance antenna having an even wider bandwidth is also developed. Prototypes of the two antennas are fabricated and measured. With a low profile of 0.03 lambda(0) (wavelength in free space), the triple-resonance design has a bandwidth of 15.2% and a peak gain of 4.80 dBi, and the quad-resonance design has a bandwidth of 17.5% and a peak gain of 7.27 dBi.