A Wideband Low-Profile Microstrip MIMO Antenna for 5G Mobile Phones
Bo Cheng, Zhengwei Du
Abstract
A wideband low-profile eight-element microstrip multiple-input–multiple-output (MIMO) antenna for fifth-generation (5G) mobile phones is proposed. The antenna is designed to be integrated on the back-cover of a mobile phone without occupying its inner space or ground clearance. The elements of the MIMO antenna can simultaneously excite the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> , TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> , TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> , and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> modes, and their broad operating bands come from combining the four modes together. The proposed MIMO antenna which is a simple single-layer plane structure with a thickness of only 0.787 mm is fabricated and tested. The experimental results show that the −6 dB impedance operating band of the MIMO antenna is 4.4–5.04 GHz which can cover the 5G N79 band of 4.4–5 GHz. It achieves a broad relative bandwidth of 13.6% with a low profile of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.01~\lambda _{0}$ </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 of the center frequency. It has an efficiency of higher than 42%, the mutual coupling of lower than −18 dB, the envelope correlation coefficients (ECCs) of lower than 0.24, and the ratios of mean effective gains (MEGs) of lower than 1.96 dB in the operating band.