Broadband Substrate Integrated Waveguide Cavity-backed Drum-shaped Slot Antenna

A new type of broadband antenna with a substrate integrated waveguide (SIW) cavity as a carrier, drum-shaped slot and shorting vias working in the X-band is designed. Due to the strong loading effect of the drum-shaped slot etched on the SIW cavity, hybrid modes (odd-TE210 and even-TE210) are generated to replace the original TE210 mode. Further, shorting vias is added in the middle of the cavity to perturb the fundamental mode without affecting the higher-order modes. These three modes (half-TE110, odd-TE210 and even-TE210) are close together so that the antenna obtains a very wide working bandwidth. The performance of the antenna was verified by simulation and experiments. The experimental fractional bandwidth (FBW) is 23.5% (8.8 - 11.15 GHz) and the maximum gain is 6.5 dBi in the working frequency. Moreover, the antenna has a very low cross-polarization level (less than - 26 dB). These excellent characteristics enable the proposed antenna suitable for X-band applications.