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

Kentaro MURATA  Naoki HONMA  Kentaro NISHIMORI  David M. KLYMYSHYN  Hisashi MORISHITA  

Publication
IEICE TRANSACTIONS on Communications   Vol.E99-B   No.1   pp.69-80
Publication Date: 2016/01/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2015ISP0028
Type of Manuscript: Special Section PAPER (Special Section on Recent Progress in Antennas, Propagation and Wireless Systems Related to Topics in ISAP2014)
Category: Antennas and Propagation
Keyword: 
short-range MIMO,  eigenmode transmission,  180-degree hybrid coupler,  

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Summary: 
An analog-beamforming-based eigenmode transmission technique is proposed that employs a network of interconnected 180-degree hybrid couplers at both transmitting and receiving sides of a plane-symmetrically 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 -28.3dB on average compared to desired signal power, and the ability to realize four-stream 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.