| 摘要 |
<p>Provided is an acoustic wave filter device with a very steep filter characteristic. An acoustic wave filter device (1) is provided with a longitudinally coupled resonator acoustic wave filter portion (20). The longitudinally coupled resonator acoustic wave filter portion (20) comprises a first to third IDT electrodes (21-23) each comprising multiple electrode fingers (21f-23f, 21h-23h), and a first and second reflectors (24, 25). Each of the first to third IDT Electrodes (21-23) comprises, at an end thereof adjacent to another IDT electrode in the direction of propagation of an acoustic wave, a narrow-pitch portion (21c, 22c, 22d, 23c) in which the pitch of electrode fingers is narrower than the pitch of electrode fingers in the remaining portion of the IDT electrode. The number of electrode fingers (22f, 22h) in the narrow pitch portion (22c) located on the first IDT electrode (21) side of the second IDT electrode (22) and the number of electrode fingers (22f, 22h) in the narrow pitch portion (22d) located on the third IDT electrode (23) side of the second IDT electrode (22) are different from each other.</p> |
