Design of a Circularly Polarized 4-element MIMO Antenna for 5G Sub-6 Band Applications

A 4-element multiple-input-multiple-output (MIMO) antenna, which has circular polarization (CP), is presented in this paper for 5G sub-6 band applications. In the arrangement of MIMO antenna, a single element has a square shaped microstrip patch antenna with 2 diagonally truncated corners, a quarter-wave transformer, a microstrip line, and an inverted T-shape slot in the ground. The purpose behind the use of two truncated corners is for CP, and a quarter-wave transformer is placed for better matching of impedance. In this MIMO configuration, each antenna is set up with the next adjacent antenna orthogonally. 4 inverted T-shape slots in the ground layer and the orthogonal positions are to provide high isolation. The placement of the slots helps to expand the axial ratio's bandwidth in single as well as MIMO antennas. The reflection coefficient and the axial ratio of the MIMO antenna are -73.34 dB and 0.97 dB, respectively. It provides an isolation value of <-35 dB along with gain values of 7.59 dBic and 7.62 dBic. The results of the diversity gain (above 9.985 dB) and envelope correlation coefficient (<0.003) are satisfactory. CST software is utilized for both design and simulation.