A 12-Port Circularly Polarized Dual-Band Back-Cover MIMO Antenna for 5G Smartphones

This letter presents a compact circularly polarized dual wide-bands twelve port multiple-input–multiple-output antenna for mobile terminal communications. It can be fitted into a smartphone as a back cover without occupying internal space. A single antenna module consists of a coaxial line feed port and a radiation patch with dimensions of 0.484<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula><inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \times 0.591\lambda _{0}$</tex-math></inline-formula><inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\times 0.0203\lambda _{0}$</tex-math></inline-formula> (where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula> is the free-space wavelength at 5 GHz). The measurement results indicate −6 dB bandwidths of 1.1 GHz (2.1 GHz to 3.2 GHz) and 0.5 GHz (5 GHz to 5.5 GHz), respectively. Significant isolation <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\geq$</tex-math></inline-formula> 18 dB, improved gain, and efficiency are achieved due to the introduction of the coronary stent-shaped-inspired metamaterial. The envelope correlation coefficient, the ratio of mean effective gains, and the efficiency are measured to be below 0.05, within 1 dB, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\geq$</tex-math></inline-formula> 90%, respectively. It also considers how the human hands impact the antenna's function. It operates over long-term evolution (LTE Band-1), LTE Band-40, worldwide interoperability for microwave access, LTE Band 41, NR Band n77, Wi-Fi 5 (802.11ac), Wi-Fi 6 (802.11ax), and NR Band n258.