A Compact Eighteen-Port Antenna Cube for MIMO Systems

An 18-port compact antenna cube is proposed in this paper. The cube, which has a volume of 0.76 × 0.76 × 0.76 λ₀³, provides 18 individual channels and is ideal for multiple-input multiple-output (MIMO) wireless communications. On each of the total six faces of the cube, a three-port tri-polarization antenna is installed. All antennas adopt a metal backing configuration, so the ground of all antennas forms a well shield Faraday cage, in which other functional circuits can be installed. Experimental measurements were carried out to evaluate the performance of the antenna cube in different MIMO scenarios. The results show that MIMO systems with the proposed compact antenna cube outperform those with dipole antennas which occupy the same number of RF channels but with much larger space. When a vertical 3-dipole array, a horizontal 3-dipole array and a dual polarization antenna are used in the user end (UE), respectively, the capacity of the global selected MIMO systems with antenna cube is about 2.7, 4.6, and 2.9 bits/s/Hz more than the full MIMO systems with a vertical 3-dipole array as the access point (AP) antennas. It is 1.9, 3.9, and 2.0 bits/s/Hz more than the full MIMO systems with a vertical 5-dipole array as AP antennas. The performance differences between the MIMO systems using global and simplified selection circuits are small.