| 摘要 |
PROBLEM TO BE SOLVED: To provide an acoustic wave filter device that has steep filter characteristics. ! SOLUTION: An acoustic wave filter device includes a longitudinally coupled resonator type acoustic wave filter part 20. The longitudinally coupled resonator type acoustic wave filter part 20 has first to third IDT electrodes 21-23 having pluralities of electrode fingers 21f-23f, and 21h-23h, and first and second reflectors 24, 25. The respective first to third IDT electrodes 21-23 have narrow-pitch parts 21c, 22c and 22d, 23c, where electrode fingers are smaller in cycle than electrode fingers at the remaining parts of the IDT electrodes, at end parts adjoining other IDT electrodes in an acoustic wave propagation direction. The number of electrode fingers 22f and 22h of the narrow-pitch part 22c which is positioned on the first IDT electrode 21 side of the second IDT electrode 22 and the number of electrode fingers 22f and 22h of the narrow-pitch part 22d which is positioned on the third IDT electrode 2 |
