Wideband Substrate Integrated Waveguide Antenna for Full-Duplex Systems

In this letter, a low-profile and wideband substrate integrated waveguide (SIW) antenna is proposed and validated for full-duplex systems. The proposed antenna operates at 4.9 GHz and 5.8 GHz Wireless Local Area Network (WLAN) bands. Each resonator of the antenna consists of a modified half-mode SIW (HMSIW) cavity, and excited by a 50 $\Omega$ coaxial probe. The wideband response is achieved by coupling the fundamental TE\textsubscript{10} mode with the perturbed TE\textsubscript{10} mode of the HMSIW cavity. The compactness of the proposed design is obtained using two rectangular slots near the closed-ends of the cavities. By properly optimizing the overall geometry, the proposed design exhibits a 10-dB fractional bandwidth of 8.2 \% (4.78--5.2 GHz) and 7.7 \% (5.70--6.16 GHz) in the lower (4.9 GHz) and upper frequency band (5.8 GHz), respectively. The bandwidths of both frequency bands can be controlled by adjusting the coupling between modes. A high isolation ( $>$ 30 dB) between the two ports is observed due to series of metallic vias between them. This antenna has compact size (0.34 $\lambda_{g}^{2}$ ) with high gains of 5.24 dBi and 5.37 dBi at 4.9 GHz and 5.8 GHz, respectively.