| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact filter. SOLUTION: The filter 10 has a line 20 which connects an input terminal 21 and an output terminal 22, a resonator 30 which is connected to the line 20, and a reactance element 40 which is connected to the line 20. The resonator 30 includes a pair of resonators 31 and 32 which are inter-digital connected, and a short-circuit terminal of the resonator 31 is connected to the line 20. At passing frequencies of the filter 10, the resonator 30 and the reactance element 40 form an equivalent parallel resonant circuit between the line 20 and the ground. At a cutoff frequency of the filter 10, the resonator 30 forms an equivalent series resonant circuit between the line 20 and the ground. Thereby, the degree of connection of the pair of resonators 31 and 32 is strengthened, so that the physical size of the resonator 30 is greatly reduced. COPYRIGHT: (C)2008,JPO&INPIT
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