Analog eigenmode transmission for 2×2 short-range MIMO

This paper proposes an analog eigenmode transmission technique for 2×2 short-range MIMO using only 180-degree hybrid couplers. When a whole short-range MIMO array is configured in line-of-sight and symmetrically with respect to specific reference planes, the channel matrix in the system also becomes symmetrical. Then, the channel matrix is diagonalized by connecting 180-degree hybrid couplers to both Tx and Rx arrays, that is, eigenmode transmission is realized by analog beam-forming. Experimental results show that this proposed method can orthogonalize channels regardless of the array configuration, such as type of antennas, antenna spacing and Tx-Rx distance as long as the symmetry of system configuration is assured.