Study of dual-polarized omni-directional antennas for 5.2 GHz-band 2×2 MIMO-OFDM systems

WLAN systems that use the MIMO-OFDM scheme, which enables high-speed transmission of over 100 Mbps, have been developed and are attracting much attention. The paper proposes novel dual-polarized omni-directional antennas as both the base station and personal station antennas for 5.2 GHz-band 2×2 MIMO-OFDM systems. The structure of the proposed antennas and their fundamental characteristics, such as input impedance and radiation pattern, are shown. The proposed antennas have overall dimensions of about 10 mm (diameter) and 50 mm (height) and so are very suitable for commercial use. It has been clarified that the shapes of their radiation patterns in the horizontal plane depend on their position relative to the notebook PC: the changes in radiation pattern depend mainly on the main-polarization component. Propagation measurements have been carried out in a typical office using an OFDM-MIMO channel measurement system and the channel capacities of a 2×2 OFDM-MIMO channel with the different antenna arrangements were elucidated.