| 摘要 |
PROBLEM TO BE SOLVED: To provide a stack filter of high attenuation quantity, which can be applied to the stack filter used for a high-frequency unit of a portable tele phone or the like and which has a form similar to a conventional one. SOLUTION: The stack filter has plural resonator electrodes 102, an inter- stage coupling capacitor electrode 104 coupling adjacent resonators and two input/output coupling capacitor electrodes 105 which couple an input/output terminal electrode 108 and the resonator electrodes. A capacitor electrode 106, which electrically connects one input/output terminal and a part of the input/ output coupling capacitor electrode, is installed. A parallel circuit is constituted of the input/output coupling capacitor electrodes and the capacitor electrodes, and the parallel resonance circuit is formed between the input/output terminals. Thus, one other attenuation pole can be formed, in addition to the attenuation pole the one inter-resonator electromagnetic filed coupling and inter-stage capacity form. Then, the stack filter of high attenuation quantity can be realized having a form similar to the conventional types.
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