| 摘要 |
A longitudinally-coupled resonance type surface-acoustic-wave filter device is provided with features in which the filter device has a sufficient band pass width, an attenuation quantity can be expanded in an elimination band on a lower band side of the pass band, a filter characteristic steepness can be increased, and an insertion loss in the pass band can be reduced. A five-IDT type and longitudinally coupled resonance type surface acoustic wave filter device (1) comprises a first IDT (11), a second IDT (12) and a third IDT (13) which are disposed on both sides with respect to a surface acoustic wave propagating direction, respectively, and a fourth IDT (14) and a fifth IDT (15) which are disposed on most outer sides with respect to a surface-acoustic-wave propagating direction, respectively. Let the number of electrode fingers and a pitch of the electrode fingers in the first IDT (11) be N1 and P1, respectively, the number of electrode fingers and a pitch of the electrode fingers in the second and third IDTs (12) and (13) be N2 and P2, respectively, and the number of electrode fingers and a pitch of the electrode fingers in the fourth and fifth IDTs be N3 and P3, respectively, and relations N1<N2<N3, and P1<P2 and P1<P3 are satisfied in the longitudinally-coupled resonance type surface-acoustic-wave filter device (1). |
