Quad-port mm-wave MIMO antenna with a unified ground plane for 5G and beyond applications

In this paper, a four-element dual-band mm-wave multiple-input-multiple-output (MIMO) antenna is proposed for the n258 and n260 5G bands. The antenna is made up of simple ring-shaped radiators, with a cross-shaped structure loaded into the ground surface to improve isolation and connect the ground planes. A common ground in the presented MIMO antenna ensures uniform current flow across the entire ground surface while preventing unwanted resonances or parasitic modes caused by disconnected grounds. A unified ground also ensures that all resonating elements and associated circuitry use the same reference voltage, which is vital for RF front-end performance. Three MIMO configurations of the proposed antenna are presented, each with a different orientation of the antenna element. The best isolation is obtained by arranging antenna elements orthogonally to one another. The presented antenna offers good matching in both bands, with impedance bandwidths of 23.8 to 25.4 GHz and 37 to 40.5 GHz. The antenna offers simulated peak gain values of 7.7 dBi and 9 dBi, while the corresponding measured gain values are 7.3 dBi and 8.5 dBi at 24 GHz and 39 GHz, respectively. In addition, the suggested antenna exhibits a high radiation efficiency ranging from approximately 94% to 99%, with an average efficiency around 97.5% across the operating band. The proposed mm-wave MIMO antenna with a shared ground offers a more mechanically robust antenna design, which could be useful for multilayer PCBs or mobile/wearable 5G and beyond applications.