Acoustic wave filter device and multiplexer using same

1. An acoustic wave filter device comprising:

a first terminal;

a second terminal;

an inductor connected to the first terminal; and

a longitudinally coupled resonator coupled between the inductor and the second terminal; wherein

the longitudinally coupled resonator includes:

at least one first IDT electrode coupled to the first terminal; and

at least one second IDT electrode connected to the second terminal;

a total capacitance value of the at least one first IDT electrode is greater than a total capacitance value of the at least one second IDT electrode;

each IDT electrode of the at least one first IDT electrode includes a first region in which electrode fingers are provided with a first pitch therebetween and a second region in which electrode fingers are provided with a second pitch therebetween, which is shorter than the first pitch;

each IDT electrode of the at least one second IDT electrode includes a third region in which electrode fingers are provided with a third pitch therebetween and a fourth region in which electrode fingers are provided with a fourth pitch therebetween, which is shorter than the third pitch;

the second region faces the fourth region; and

a number of electrode fingers adjacent to each other with the second pitch therebetween in the second region is greater than a number of electrode fingers adjacent to each other with the fourth pitch therebetween in the fourth region.

2. The acoustic wave filter device according to claim 1 , wherein a total number of electrode fingers of the at least one first IDT electrode is greater than a total number of electrode fingers of the at least one second IDT electrode.

3. The acoustic wave filter device according to claim 1 , wherein the at least one first IDT electrode includes an IDT electrode including a number of electrode fingers greater than a number of electrode fingers of each of the at least one second IDT electrode.

4. The acoustic wave filter device according to claim 1 , wherein a number of electrode fingers of each IDT electrode included in the at least one first IDT electrode is greater than a number of electrode fingers of each IDT electrode included in the at least one second IDT electrode.

5. The acoustic wave filter device according to claim 1 , wherein an electrode-finger-to-electrode-finger distance of the at least one first IDT electrode is shorter than an electrode-finger-to-electrode-finger distance of each of the at least one second IDT electrode.

6. The acoustic wave filter device according to claim 1 , wherein the longitudinally coupled resonator is an acoustic wave resonator.

7. The acoustic wave filter device according to claim 1 , further comprising a resonator connected between a connection node between the inductor and the longitudinally coupled resonator and a ground potential.

8. A multiplexer comprising:

the acoustic wave filter device according to claim 1 .

9. An acoustic wave filter device comprising:

a first terminal;

a second terminal;

an inductor connected to the first terminal; and

a longitudinally coupled resonator coupled between the inductor and the second terminal; wherein

the longitudinally coupled resonator includes:

at least one first IDT electrode coupled to the first terminal; and

at least one second IDT electrode connected to the second terminal;

a total area of an intersecting region of electrode fingers of the at least one first IDT electrode is larger than a total area of an intersecting region of electrode fingers of the at least one second IDT electrode;

each IDT electrode of the at least one first IDT electrode includes a first region in which electrode fingers are provided with a first pitch therebetween and a second region in which electrode fingers are provided with a second pitch therebetween, which is shorter than the first pitch;

each IDT electrode of the at least one second IDT electrode includes a third region in which electrode fingers are provided with a third pitch therebetween and a fourth region in which electrode fingers are provided with a fourth pitch therebetween, which is shorter than the third pitch;

the second region faces the fourth region; and

a number of electrode fingers adjacent to each other with the second pitch therebetween in the second region is greater than a number of electrode fingers adjacent to each other with the fourth pitch therebetween in the fourth region.

10. The multiplexer according to claim 8 , further comprising:

a third terminal; and

a filter device between the first terminal and the third terminal.

11. The acoustic wave filter device according to claim 9 , wherein a total number of electrode fingers of the at least one first IDT electrode is greater than a total number of electrode fingers of the at least one second IDT electrode.

12. The acoustic wave filter device according to claim 9 , wherein the at least one first IDT electrode includes an IDT electrode including a number of electrode fingers greater than a number of electrode fingers of each of the at least one second IDT electrode.

13. The acoustic wave filter device according to claim 9 , wherein a number of electrode fingers of each IDT electrode included in the at least one first IDT electrode is greater than a number of electrode fingers of each IDT electrode included in the at least one second IDT electrode.

14. The acoustic wave filter device according to claim 9 , wherein an electrode-finger-to-electrode-finger distance of the at least one first IDT electrode is shorter than an electrode-finger-to-electrode-finger distance of each of the at least one second IDT electrode.

15. The acoustic wave filter device according to claim 9 , wherein the longitudinally coupled resonator is an acoustic wave resonator.

16. The acoustic wave filter device according to claim 9 , further comprising a resonator connected between a connection node between the inductor and the longitudinally coupled resonator and a ground potential.

17. A multiplexer comprising:

the acoustic wave filter device according to claim 9 .

18. The multiplexer according to claim 17 , further comprising:

a third terminal; and

a filter device between the first terminal and the third terminal.