| 摘要 |
PROBLEM TO BE SOLVED: To provide an antenna system where radio wave transmission with less fading and attenuation can be attained without the need for installing a leakage coaxial cable in a confined space such as a tunnel. SOLUTION: A plurality of transmission antennas 21 and 22 having unidirectivity whose radiation power pattern half-value angle is 70 degrees or below are placed sequentially so that the other transmission antenna 22 is placed within the radiation power pattern half-value angle of the transmission antenna 21 in the same direction. Furthermore, the transmission antenna 22 is placed at a position at which attenuation of a radio wave emitted by the transmission antenna 21 is 3dB or over. Thus, the antenna system has a function of matching base of radio waves emitted from each of the transmission antennas 21, 22 with the phase of a radio wave emitted from the other transmission antenna so as to avoid the interference between them.
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