A Wideband Low-Profile Microstrip MIMO Antenna for 5G Mobile Phones

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
₀₁
, TM
₁₀
, TM
₀₂
, and TM
₁₁
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
$0.01~\lambda _{0}$
, where
$\lambda _{0}$
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.