| 摘要 |
A multiple frequency band antenna includes a dipole antenna ( 4 a), which is formed of two dipole antenna elements ( 8 a , 10 a). Two extension elements ( 24 a , 26 a) extend outward from respective ones of opposed outer ends of the dipole antenna ( 4 a). The length of the dipole antenna ( 4 a) is determined to make the multiple frequency band antenna capable of receiving radio waves in the UHF band, and the sum of the lengths of the dipole antenna ( 4 a) and the extension elements ( 24 a , 26 a) is determined to make the multiple frequency band antenna capable of receiving radio waves in the VHF band. PIN diodes ( 28 a , 34 a) are connected between the respective extension elements ( 24 a , 26 a) and the respective outer ends of the dipole antenna ( 4 a). When a radio wave in the UHF band is to be received, a control unit ( 180 ) places the diodes ( 28 a , 34 a) selectively in a state in which both are opened, a state in which one of the diodes ( 28 a) is closed while the other ( 34 a) is opened, and a state in which the one diode ( 28 a) is opened while the other ( 34 a) is closed.
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