| 摘要 |
PROBLEM TO BE SOLVED: To provide a center frequency band variable type band pass filter capable of fixing the position of a stop area even at the time of changing the center frequency of a pass band. SOLUTION: This band pass filter is provided with input and output terminals A1 and A2 connected through first and second coupling capacities C1 and C2 so that one of them can be turned into an input terminal while the other can be turned into an output terminal, a first parallel resonance circuit K1 connected through a third coupling capacity C3 to one input and output terminal A2 in parallel to the second coupling capacity C2, and a second parallel resonance circuit K2 connected to the connection of the first and second coupling capacities C1 and C2. Then, first and second variable capacity diodes CV1 and CV2 are respectively used for the first and second parallel resonance circuits K1 and K2.
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