Wideband Tripolarized MIMO Antenna With Pattern Diversity for 5G Application

Abstract

A compact wideband tripolarized multiple-input–multiple-output (MIMO) antenna with pattern diversity is proposed and measured. A monopole-equivalent structure with a large gap is designed for vertically polarized (VP) omnidirectional radiation pattern, while circular and ring patches are designed for two horizontally polarized broadside radiation patterns. The three polarizations are mutually orthogonal. Shorting pins are uniformly distributed under the ring patch, bringing the resonant frequencies of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> modes closer together and increasing the bandwidth of the monopole mode. For patch mode, the circular and ring patches can generate three adjacent resonant frequencies by using a pair of metal strips with equal amplitude inverted signal, resulting in a broader bandwidth. The measured <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -parameters and radiation patterns are consistent with the simulated ones. The proposed antenna exhibits an overlapped bandwidth of 45.8% (2.98–4.75 GHz) with a low profile (0.125 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ). Within the operational impedance bandwidth, the peak gains are 5.1 and 9 dBi for the omnidirectional and broadside modes, respectively.