MIMO capacity comparison between the ideal and realistic tri-polarized dipole and loop antennas

In this paper, the 3 × 3 multiple-input-multiple-output (MIMO) capacities composed of the ideal and the realistic co-located tri-polarized dipole (TPD) and tri-polarized loop (TPL) antennas are investigated, in the free space (FS) channel and the parallel perfect electric conductor (PEC) two-mirror (TM) channel, separately. In the FS channel, with the same communication distance, the capacity gain patterns of the realistic and ideal tri-polarized antennas are distinctly different due to the difference in radiation patterns. Furthermore, the ideal TPD capacity gains are slightly larger than the realistic antennas. In the TM channel, the contour plots of the capacity gain are similar with same communication distance. Additionally, the realistic TPL capacity gains are better than the ideal TPD and the realistic TPD antenna by 5% and 10%, respectively. Through the comparison, it is obvious to see that the channel capacity gains in TM are larger than it in FS over 20% due to the multipath reflections. Moreover, the maximum capacity gain can be 3 in the TM and 2.2 in FS channel only.