Design of a mine high isolation tri-band MIMO antenna

Due to space limitations, multi frequency multiple-input multiple-output (MIMO) antennas have strong coupling problems caused by small unit spacing. In order to solve the above problems, a mine high isolation tri-band MIMO antenna has been designed. By loading two L-shaped branches at both ends of a rectangular branch to form a trident monopole antenna, the antenna has tri-band features. Two trident monopole antenna units are placed symmetrically. A T-shaped branch is loaded on the metal floor between the two units. The opposite current generated by parasitic branches is used to offset the coupling current without branches. Two symmetrical rectangular slots are etched to suppress the mutual coupling caused by surface waves on the floor by changing the current distribution on the floor. The high isolation of the antenna throughout the entire band is achieved. The simulation results show that the antenna operates in frequency bands of 1.85-2.70, 3.24-3.99, 4.65-5.80 GHz, can effectively covering coal mines' underground WiMAX/WiFi/4G/5G NR operating band. The isolation of the antenna in three bands is greater than 20, 22, 22 dB, respectively. It is 11, 9, 10 dB higher than the isolation of the antenna before decoupling; The envelope correlation coefficient is less than 0.2, indicating good diversity performance. The antenna has stable gain variation within the operating band and good omnidirectional radiation features. This antenna has the advantages of simple and compact structure, easy processing, and low profile. It has a wide range of application scenarios in wireless communication in coal mines.