Broadband Planar SIW Cavity-Backed Slot Antennas Aided by Unbalanced Shorting Vias

Abstract

Two types of substrate integrated waveguide (SIW) cavity-backed slot (CBS) antennas are proposed for bandwidth enhancement. First, a quad-resonance SIW CBS antenna is proposed using a cross-shaped slot and loading unbalanced shorting vias. Additional half- $\textrm {TE}_{120}$ mode is successfully excited along with three other independent modes including half- $\textrm {TE}_{110}$ and odd and even $\textrm {TE}_{210}$ modes. Next, a penta-resonance SIW CBS antenna with a cross-shaped slot is proposed, in which two pairs of shorting vias are loaded. Two additional hybrid modes of half- $\textrm {TE}_{210}$ and half- $\textrm {TE}_{120}$ modes are introduced along with three other independent modes including half- $\textrm {TE}_{110}$ and odd and even $\textrm {TE}_{310}$ modes. Furthermore, the working mechanism of these two types of SIW CBS antennas is explained. Finally, prototypes of these two antennas are fabricated and measured at X -band. Their measured fractional bandwidths are $\text{20.0}\%$ and $\text{20.8}\%$ , respectively. Simulation and measurement results agree very well, which confirms the validity of the proposed designs.