| 摘要 |
PROBLEM TO BE SOLVED: To implement an antenna system which is compact and allows impedance matching according with the use state of an antenna not to degrade communication performance. SOLUTION: The antenna device includes a loop antenna of which the antenna element length is shorter in comparison with a wavelength of a frequency band for use, a first matching circuit 2 connected to one feed part of the loop antenna 1; a second matching circuit 4 connected to the other feed part of the loop antenna 1, a RF circuit 3 for feeding the loop antenna 1, a power detection circuit 6 for detecting reflected power from the loop antenna 1, and a control circuit 5 for controlling the second matching circuit 4 on the basis of a detection value of the power detection circuit 6. COPYRIGHT: (C)2008,JPO&INPIT
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