Kentaro Murata

Analog Eigenmode Transmission for Short-Range MIMO

This paper proposes a method of implementing analog eigenmode transmission for a short-range multiple-input-multiple-output (SR-MIMO) system that uses only 180° hybrid couplers. If the short-range MIMO system places transmitting and receiving arrays in line-of-sight (LOS) and symmetrically with respect to specific reference planes, the channel matrix in the system also becomes symmetrical. This allows the channel matrix to be diagonalized by connecting 180° hybrid couplers to both ports at the transmitter and receiver sides, i.e., eigenmode transmission can be realized. In this paper, first, the theory of the proposed technique is explained by taking a 2

Interference reduction between SDD linear array antennas using end-fire arrangement

\times

Analog eigenmode transmission for 2×2 short-range MIMO

2 MIMO as an example, based on the characteristics of 180° hybrid coupler and the theory of the cascade-connected network. Moreover, an extension to the method that offers 4

Analog Eigenmode Transmission for Short-Range MIMO Based on Orbital Angular Momentum

\times

Performance of miniaturized 6-port MIMO antenna using orthogonal polarization

4 MIMO is also proposed. This paper clarifies that this proposed technique can diagonalize the channel matrix, regardless of array configuration, such as type of antennas and antenna spacing, as long as the symmetry of the system configuration is assured. Furthermore, numerical results verify that the distance between the transmitter and the receiver has no effect on channel orthogonality. As a result, this technique partially avoids the performance degradation caused by array displacement, which is a major disadvantage of the conventional analog-beamforming-based decoding technique for short-range MIMO systems. Thus, the superiority of the proposed technique is clear.

Antenna Arrangement Suitable for Full-Duplex MIMO

This paper proposes a self-interference reduction method exploiting antenna arrangement and beamforming for space division duplex (SDD) relay station. When transmitting (Tx) and receiving (Rx) linear array antennas are placed in end-fire arrangement, spatial correlation between Tx and Rx increases. This causes rank degeneracy of the channel matrix between Tx and Rx. With this channel, almost all the self-interference inside SDD relay station can be reduced by forming beam to the nearly-zero space at Tx. Simulation results show that there is the optimum element spacing of linear array, and that the proposed method greatly improves channel capacity of SDD relay system, which is higher than that of the time division duplex (TDD) system.

On potential channel capacity of massive MIMO array within small finite space

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.

Eigenmode decoupling technique exploiting symmetric antenna arrangement

This paper proposes an analog eigenmode transmission technique suitable for a short-range multiple-input multiple-output (SR-MIMO) system consisting of arbitrary power-of-two number of antennas utilizing the idea of orbital angular momentum. In the proposed technique, uniform circular arrays that are coaxially arranged are used at both the transmitting (Tx) and receiving (Rx) sides. With this array configuration, the channel matrix is always a circulant matrix regardless of antenna type, array radius, Tx–Rx distance, and rotation about the coaxis. Due to the characteristics of a circulant matrix, the channel matrix can be diagonalized independently of the above-mentioned factors by fixed-weight beamforming based on a discrete Fourier transform (DFT) matrix uniquely determined by just the number of antennas. In this paper, the operating principle of the proposed technique is discussed from the viewpoints of linear algebra, and some example network configurations are presented with the determination of the DFT-matrix weight. Numerical analyses confirm the two important features of the proposed technique: 1) support of more than

Parts transporting tray

4\times 4

Analog-digital hybrid eigenmode transmission for massive short-range MIMO

SR-MIMO and 2) independence with regard to rotation about the coaxis. Furthermore, an experiment on a fabricated DFT circuit confirmed the feasibility of the proposed technique in realizing practical short-range communication.