| 摘要 |
PROBLEM TO BE SOLVED: To provide a filter apparatus having a steep attenuation characteristic for a narrow bandwidth. SOLUTION: The filter apparatus consists of circuit components formed on a single board 11, and the components includes: a series arm 14 formed between an input signal electrode 12 and an output signal electrode 13; resonators 15a, 15b, 15c having a prescribed resonance frequency located on the series arm 14; parallel arms 17a, 17b, 17c, 17d formed between the series arm 14 and ground electrodes 16; and resonators 18a, 18b, 18c, 18d located on the parallel arms 17a, 17b, 17c, 17d and having an anti-resonance frequency for forming the pass band with the resonance frequency of the resonators 15a, 15b, 15c, wherein an effective electromechanical coupling coefficient of the resonator 18a is made different from effective electromechanical coupling coefficients of the other resonators 15a, 15b, 15c, 18b, 18c, 18d. COPYRIGHT: (C)2005,JPO&NCIPI
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