| 摘要 |
PROBLEM TO BE SOLVED: To provide a small and staged ladder filter which is easily designed. SOLUTION: A unit is formed by inserting a metallic terminal plate 34 between the upper surface electrode of a bending resonator 61 becoming a serial resonator and the lower surface electrode of a bending resonator 71 becoming a parallel resonator for piling them. Two sets of these units are disposed planar on a substrate 32, and a metallic cover 33 is placed on the substrate 32 so as to cover these units. By the conductive pattern of the substrate 32, the lower surface electrode of the resonator 61 of the unit of the first stage is connected to an input terminal 44, the plate 34 of the unit of the first stage is connected to the lower surface electrode of the resonator 61 of the unit of the next unit, and the plate 34 of the unit of the next stage is connected to an output terminal 46. Further, the upper surface electrodes of the resonators 71 of the respective units are continued to each other with a cover 33.
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