| 摘要 |
PROBLEM TO BE SOLVED: To provide a piezoelectric filter in which selectivity can be improved without causing out-of-band attenuation to deteriorate. SOLUTION: In the piezoelectric filter, the output part of a first three- terminal filter element F1 is connected with the input part of a second three- terminal filter element F2 , and an interconnecting capacity Cr is connected between the grounding part and the input part of the interconnected first three- terminal filter element F1 and second three-terminal filter element F2 . Selectivity as the filter characteristics is improved, by connecting an additional capacity Co between the input part and the output part of either of the three-terminal filter elements F2 .
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