A Compact Four-Port MIMO Antenna with Wideband Operation

This paper presents a 4-port multiple-input-multiple-output (MIMO) antenna with wideband operation, high isolation, as well as compact size characteristics. A MIMO element consists of a 50-Ω microstrip feeding line, a slotted ground, and a metasurface (MS). The MS layer of the MIMO element consists of four cells arranged in a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2\times 2$</tex> configuration. For MIMO design, four MIMO elements are also arranged in a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2 \times 2$</tex> configuration and decoupled by using shorting pins. The optimal design has a compact size of 1.07 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\lambda \times 0.89 \lambda \times 0.07 \lambda$</tex> and center-to-center element spacing of 0.35 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\lambda$</tex> at 5.2 GHz. The simulated operating bandwidth is 20.5% (4.8-5.9 GHz) with isolation of better than 20 dB and peak gain of 4.9 dBi.