Design of a two-port UWB MIMO antenna with high isolation based on characteristic mode theory

In this paper, a two-port ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna is designed, fabricated, and tested based on characteristic mode theory. The MIMO design consists of two circular patches which are connected to the UWB unit with an I-shaped branch. Slots are opened in the circular patch to enhance the impedance matching performance, and in order to improve the isolation of the antenna while operating, metal strips are added to the patch, and a fence decoupling structure. The overall size of the proposed antenna is 77.5 × 39 × 1 mm3, and the microstrip feed is used. Simulation results show that the antenna can cover the 2.68-11.85 GHz band with a return loss of -43.5 dB, an isolation of less than -20 dB, and an envelope correlation coefficient (ECC) of