| 摘要 |
To provide a longitudinally-coupled-resonator surface acoustic wave filter device having a sufficient pass-band width, in which a large attenuation in a stop band near the low-frequency side of a pass band and sharp filter characteristics can be obtained, and low insertion loss in the pass band can be achieved. There is provided a five-IDT longitudinally-coupled-resonator acoustic wave filter device (1) including a first IDT (11), second and third IDTs (12 and 13) disposed on either side of the first IDT (11) in a direction of propagation of surface waves, and fourth and fifth outermost IDTs (14 and 15) in the direction of propagation of surface waves, wherein when the first IDT (11) has the number of electrode fingers N1 and an electrode finger pitch P1, the second and third IDTs (12 and 13) have the number of electrode fingers N2 and an electrode finger pitch P2, and the fourth and fifth IDTs have the number of electrode fingers N3 and an electrode finger pitch P3, a relationship of N1 < N2, N1 < N3, P1 < P2, and P1 < P3 is satisfied. |
