Compact Four-Element Quarter Mode Circular SIW Based MIMO Antenna with Enhanced Isolation

A 4-port quarter-mode substrate integrated waveguide (QMSIW) multi-input multi-output (MIMO) antenna with enhanced isolation is presented in this paper. The antenna is designed based on circular QMSIW cavity and the antenna elements are arranged orthogonally. Two longitudinal slots are introduced on the antenna elements to achieve simultaneous miniaturization and reduction of mutual coupling upto 45 dB. A prototype of the proposed antenna occupying an electrical size of 0.48λ0×\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda _{0} \times $$\end{document} 0.48λ0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda _{0}$$\end{document} (λ0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda _{0}$$\end{document} is the free space wavelength at the operating frequency) is fabricated operating at center frequency of 2.4 GHz. The 4-port QMSIW MIMO antenna achieves a significant gain of 3.58 dBi and 45%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\%$$\end{document} miniaturization compared to the structure without slots. The diversity performance of the proposed antenna is also verified and the MIMO antenna exhibits extremely low envelope correlation coefficient and a high diversity gain > 9 dB. The proposed 4-port MIMO antenna is a suitable candiadate for directional Wi-Fi applications.