Wideband Substrate Integrated Waveguide Antenna for Full-Duplex Systems

Abstract

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 and 5.8 GHz wireless local area network bands. Each resonator of the antenna consists of a modified half-mode SIW (HMSIW) cavity, and excited by a 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Omega$</tex-math></inline-formula> coaxial probe. The wideband response is achieved by coupling the fundamental <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm TE}_{10}$</tex-math></inline-formula> mode with the perturbed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm TE}_{10}$</tex-math></inline-formula> 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 (5.8 GHz) frequency bands, respectively. The bandwidths of both frequency bands can be controlled by adjusting the coupling between modes. A high isolation ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula> 30 dB) between the two ports is observed due to series of metallic vias between them. This antenna has compact size (0.007 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{g}^{3}$</tex-math></inline-formula> ) with high gains of 5.24 and 5.37 dBi at 4.9 and 5.8 GHz, respectively. The proposed design is suitable for emerging full-duplex systems, thanks to its small size, high isolation, wide bandwidth, and independent resonance and bandwidth control.