Dual Polarization MIMO Antenna for 5G Mobile Phone Applications

A dual-polarization microstrip multiple-input-multiple-output (MIMO) antenna for 5G mobile phone applications is proposed in this communication. Eight differentially fed microstrip antenna elements are arranged on the back cover of a mobile phone. Four shorted radiation patches constitute the radiator of an antenna pair, and four antenna pairs form an eight-element MIMO antenna. The antenna element can excite two modes by utilizing the interaction of the two elements of one antenna pair and has a wide operating band. A prototype of the MIMO antenna is fabricated, and eight power dividers are applied to provide the differential feeding. The measured -6 dB impedance operating band is 4.37-5.5 GHz and can cover the N79 band (4.4-5 GHz) for 5G. The measured efficiencies of the antenna elements with a low profile of 1.2 mm are 40%-50% in the N79 band though the substrate has a high loss tangent of 0.02. The measured results show that the MIMO antenna has low mutual couplings of lower than -22 dB, low envelope correlation coefficients (ECCs) of lower than 0.068, and the ratios of mean effective gains (MEGs) of lower than 2.28 dB. Some issues in practical applications are discussed. The proposed antenna provides a promising solution to design a compact and pony-size MIMO antenna without occupying the inner space or ground clearance of a mobile phone.