| 摘要 |
PROBLEM TO BE SOLVED: To obtain a means for reducing the insertion loss of the coupled SAW filter in which a multiple-mode SAW filter is serially connected with a SAW resonator. SOLUTION: In this coupled surface acoustic wave filter, a surface acoustic wave filter and a surface acoustic wave resonator are serially connected on a piezoelectric substrate, with the junction between them connected in parallel with an IDT electrode to increase the capacity. The normalized value of the electrode period of the IDT electrode is made higher than the normalized value of the electrode period of the surface acoustic wave filter, and in addition, as to the logarithm, the absolute value of the reflection coefficient of the IDT electrode is made larger than 0.95.
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