Optimal 2x2 Antenna Placement for Short-Range Communications

In this letter, we investigate the optimal antenna placement with path loss and phase differences in terms of the condition number in short-range communications. First, the line-of-sight (LOS) 2×2 multiple-input multiple-output (MIMO) channel matrix with path loss and phase differences is modeled using the spherical-wave model. We then derive the explicit analytical expression and the geometrical pattern for the optimal antenna placement when considering the joint effects of path loss and phase differences, which are compared with the analytical expression and the geometrical pattern when considering only the phase differences. By the optimal antenna placement, the high correlation between the LOS responses can be overcome. Analytical and numerical results show that the path loss differences for short-range communications have a significant impact on the condition number.