A Dual-CP Quad-Port MIMO Antenna With Reduced Mutual Coupling for X-Band Application

A compact quad-port multiple-input–multiple-output (MIMO) antenna with dual polarization is proposed. Each of the four antenna elements features a modified rectangular radiator backed by a partial ground plane and fed by a T-shaped microstrip line. The four antenna elements are interconnected by an X-shaped strip and isolated by a modified plus-shaped structure, resulting in over −18 dB of isolation. With a small footprint of only 36 mm × 27 mm, the antenna exhibits a 10 dB impedance bandwidth with a completely overlapping 3 dB axial-ratio bandwidth of 19.32% (7.90–9.59 GHz). Additionally, it can provide a gain of over 3.5 dBi, an efficiency of over 70%, and an envelope correlation coefficient of less than 0.01 in both isotropic and real propagation scenarios.