Four-Stream Parallel Transmission for Short-Range MIMO Using Only Passive Analog Components

Abstract

An analog-beamforming-based eigenmode transmission technique is proposed that employs a network of interconnected 180degree hybrid couplers at both transmitting and receiving sides of a planesymmetrically configured short-range MIMO system. This technique can orthogonalize MIMO channels regardless of array parameters such as antenna spacing and Tx-Rx distance, provided the MIMO array is symmetric. For verifying the effectiveness of the proposed technique in channel orthogonalization, an experiment is conducted using a 4×4 MIMO array consisting of microstrip antennas and cascade-connected rat-race hybrid couplers. The results indicate a reduction in interference by approximately −28.3 dB on average compared to desired signal power, and the ability to realize fourstream parallel MIMO transmission by using only analog passive networks. The proposed technique can achieve channel capacity almost equivalent to that of eigenbeam space division multiplexing with ideal digital beamforming.

Simultaneous Decoupling and Matching Technique for Short-Range MIMO

“…In our previous work, we focused on the characteristics of SR-MIMO, its propagation channels are uniquely determined due to its LOS configuration, and proposed an analog-beamforming-based eigenmode transmission technique [7]- [9]. In this technique, by connecting 180-degree hybrid couplers (HCs) to both Tx/Rx sides of a planesymmetrical SR-MIMO system, the MIMO channels are orthogonalized into multi independent streams using only analog passive networks which greatly reduces hardware complexity.…”