| 摘要 |
A soft magnetic member (5) which is formed by a composite of an organic object such as a metal grain powder, a flake, a ferrite grain powder, a ferrite, an amorphous film or a layered member of the amorphous film with 10 mm or lower thickness so as to satisfy a predetermined relationship with an antenna area, a circumference length, and a magnetic transmission ratio and a conductive member (7) which has approximately 10 x 10<-8> OMEGA m or lower, more preferably 0.005 OMEGA or lower initial resistance are provided between the an antenna coil which is formed at least one loop and a metal surface (6) of the conductive member such as a metal casing. The magnetic flux which invades into the conductive object is blocked by the soft magnetic member (5) and the conductive member (7) so as to restrict the influence thereof. By doing this, it is possible to provide a reader/writer antenna for an RFID system in which it is possible to restrict a variance of a resonating frequency and an increase in a loss even if it is disposed so as to contact the conductive object such as a metal casing. <IMAGE>
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