| 摘要 |
PROBLEM TO BE SOLVED: To acquire means for designing input and output impedance of a duplex mode filter in response to the impedance of circuits located before and after the circuits to be connected to a duplex mode crystal filter in an IF circuit mounting a duplex mode piezoelectric filter. SOLUTION: The duplex mode piezoelectric filter has a first electrode and a second electrode each disposed separately with a predetermined distance on a main surface of a piezoelectric substrate, and has a third electrode disposed opposing to the first and second electrodes on the other main surface. The filter is constituted so that a resonance frequency to be excited by the first electrode and the third electrode is to be set in response to the input impedance, and a resonance frequency to be excited by the second and the third electrode is to be set in response to the output impedance. COPYRIGHT: (C)2005,JPO&NCIPI
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