Design of an Optimized Four-Port MIMO Antenna with Enhanced Isolation for 5G Applications

Abstract

This paper introduces a compact rectangular patch antenna design featuring a partial ground plane on a low-cost FR4-epoxy substrate, suitable for wireless communication systems. Simulations confirm excellent single-element performance at 5.9 GHz, achieving a reflection coefficient (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$S_{11}$</tex>) below <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-57 d B$</tex>, a peak gain of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$5 d B i$</tex>, and efficiency exceeding 90%. Following a systematic optimization process, a 4-port MIMO configuration based on this element was developed. This multi-antenna system demonstrates strong performance, resonating at 5.9 GHz with a wide 4 GHz bandwidth (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$4.5-8.5 \text{GHz}$</tex> for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$S_{11}&lt;-10 d B$</tex>) and excellent inter-port isolation exceeding <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$25 d B$</tex>. The design maintains high gain and radiation efficiency (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt;90 {\%}$</tex>). Analysis of standard MIMO metrics (ECC, TARC, MEG, CCL) confirmed acceptable performance. In summary, the optimized 4-port design successfully reduces mutual coupling by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$25 d B$</tex> while preserving high gain, efficiency, and bandwidth.