| 摘要 |
PROBLEM TO BE SOLVED: To provide an antenna device which cuts off an interference wave by an antenna circuit and can be made inexpensive. SOLUTION: An antenna 1 side of a first stage LNA (low noise amplifier) 2A is provided with a high pass filter (HPF) for cutting off a general-purpose frequency adjacent to a low frequency side of a frequency band of at least use purpose as a frequency selection circuit 11A. A cutoff frequency adjacent to a lowpass side, that is, a cutoff frequency is set to 900 MHz, so that the set frequency and harmonics by the set frequency are prevented from being received as an interference wave from a frequently used general-purpose frequency band, for example, 800 to 900 MHz for portable telephone. In addition, since the need of an additional filter in the antenna circuit can be eliminated, a circuit configuration can be simplified. COPYRIGHT: (C)2007,JPO&INPIT
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