| 摘要 |
PROBLEM TO BE SOLVED: To achieve compact radio communication having high secrecy as compared with a conventional, omnidirectional antenna system, or the like when performing the authentication sequence, or the like of a radio LAN. SOLUTION: The antenna system having damped wave directivity is used for example as a subantenna system 20 that is separated from a main antenna system 10 in a portable terminal unit 1 and is built into the back side of an antenna attachment section 2-2. The subantenna system 20 comprises a coaxial cable 21 (or a coaxial connector), a metal lens barrel 22 whose aperture is 1/2 or smaller of a wavelengthλ, a metal reflector 23, and a dielectric cap 24. The metal lens barrel 22, the metal reflector 23, and the coaxial cable 21 (or the coaxial connector) are electrically connected; a center wire 21d in the coaxial cable 21 (or the coaxial connector) is exposed to a cavity 22b in the metal lens barrel 22; and the cavity 22b forms space closed by the dielectric cap 24. COPYRIGHT: (C)2006,JPO&NCIPI
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