| 摘要 |
PROBLEM TO BE SOLVED: To provide an SAW(surface acoustic wave) filter which has a high damping region near the end section of the passing band and can obtain a large damping amount in a desired frequency band. SOLUTION: In this SAW filter, a balanced SAW filter element and a ladder- type SAW filter element are cascade-connected, and the balanced SAW filter element is constituted of two kinds of SAW resonators (SAW resonators 3 and 6 and 4 and 5) in which IDT electrodes are arranged at different finger pitches, so to satisfy a relation, k1×T1 <k2×T2 , where k1 , T1 , k2 and T2 respectively represent the electrode finger crossing width and electrode finger logarithm of the resonators 4 and 5 having the larger electrode finger pitch and the electrode finger crossing width and electrode finger logarithm of the resonators having a smaller electrode finger pitch.
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