Surface acoustic wave apparatus
View Patent ↗A surface acoustic wave apparatus includes an input terminal, an output terminal, a plurality of acoustically coupled interdigital transducers (IDT), and a phase rotating element (line or inductor) connected in parallel with one or more IDT's. The acoustically coupled IDT's are connected in series between the input and output terminals. Alternatively, the acoustically coupled IDT's may include a series IDT to which the phase rotating element is connected and which is connected in series between the input and output terminals, and a branch IDT acoustically coupled to the series IDT, and disposed on a transmission path which branches from a transmission path between the input and output terminals to a reference potential. Among the plurality of IDT's, λa≧λb is established, where λa represents an electrode finger pitch of the IDT to which the phase rotating element is connected, and λb represents an electrode finger pitch of the IDT to which no phase rotating element is connected.
1. A surface acoustic wave apparatus including a signal input terminal,
a signal output terminal, a first series interdigital transducer, a second series interdigital transducer, and a branch interdigital transducer, the first and second interdigital transducers being connected in series between the signal input terminal and the signal output terminal, and the branch interdigital transducer being disposed on a transmission path which branches from a transmission path between the signal input terminal and the signal output terminal to a reference potential, wherein:
a phase rotating element is connected in parallel with said first series interdigital transducer,
said first series interdigital transducer is acoustically coupled with said second series interdigital transducer,
said first series interdigital transducer has a closer electrode finger pitch to an electrode finger pitch of said second series interdigital transducer than an electrode finger pitch of said branch interdigital transducer.
2. The surface acoustic wave apparatus according to claim 1 , wherein:
no phase rotating element is connected with said second series interdigital transducer,
λa≧λb is satisfied, where λa represents the electrode finger pitch of said first series interdigital transducer to which said phase rotating element is connected, and λb represents an electrode finger pitch of the second series interdigital transducer to which no phase rotating element is connected, among said first and second series interdigital transducers.
3. A surface acoustic wave filter including one or more of the surface acoustic wave apparatus according to claim 2 .
4. A duplexer having a common terminal connected to an antenna, and a transmission filter and a reception filter connected to said common terminal, wherein:
one or both of said transmission filter and said reception filter include the surface acoustic wave apparatus according to claim 2 .
5. The surface acoustic wave apparatus according to claim 1 , wherein:
an element value of said phase rotating element is set to satisfy Fas 1 <Frp, where Fas 1 represents an antiresonance frequency of said first series interdigital transducer to which said phase rotating eclement is connected, and Frp represents a resonance frequency of said branch interdigital transducer.
6. A surface acoustic wave filter including one or more of the surface acoustic wave apparatus according to claim 5 .
7. A duplexer having a common terminal connected to an antenna, and a transmission filter and a reception filter connected to said common terminal, wherein:
one or both of said transmission filter and said reception filter include the surface acoustic wave apparatus according to claim 5 .
8. The surface acoustic wave apparatus according to claim 1 , wherein:
said phase rotating element includes one or both of a transmission line and an inductance element.
9. A surface acoustic wave filter including one or more of the surface acoustic wave apparatus according to claim 8 .
10. A duplexer having a common terminal connected to an antenna, and a transmission filter and a reception filter connected to said common terminal, wherein:
one or both of said transmission filter and said reception filter include the surface acoustic wave apparatus according to claim 8 .
11. A surface acoustic wave filter including one or more of the surface acoustic wave apparatus according to claim 1 .
12. A duplexer having a common terminal connected to an antenna, and a transmission filter and a reception filter connected to said common terminal, wherein:
one or both of said transmission filter and said reception filter include the surface acoustic wave apparatus according to claim 1 .
13. A surface acoustic wave apparatus including a signal input terminal, a signal output terminal, a first series interdigital transducer, a second series interdigital transducer, and a branch interdigital transducer, the first and second interdigital transducers being connected in series between the signal input terminal and the signal output terminal, and the branch interdigital transducer being disposed on a transmission path which branches from a transmission path between the signal input terminal and the signal output terminal to a reference potential, wherein:
a phase rotating element is connected in parallel with said first series interdigital transducer,
said first series interdigital transducer is acoustically coupled with said branch interdigital transducer,
said first series interdigital transducer has a closer electrode finger pitch to an electrode finger pitch of said branch interdigital transducer than an electrode finger pitch of said second series interdigital transducer.
14. The surface acoustic wave apparatus according to claim 13 , wherein:
no phase rotating element is connected with said second series interdigital transducer,
λa≧λb is satisfied, where λa represents the electrode finger pitch of said first series interdigital transducer to which said phase rotating element is connected, and λb represents an electrode finger pitch of the second series interdigital transducer to which no phase rotating element is connected, among said first and second series interdigital transducers.
15. A surface acoustic wave filter including one or more of the surface acoustic wave apparatus according to claim 14 .
16. A duplexer having a common terminal connected to an antenna, and a transmission filter and a reception filter connected to said common terminal, wherein:
one or both of said transmission filter and said reception filter include the surface acoustic wave apparatus according to claim 14 .
17. The surface acoustic wave apparatus according to claim 13 , wherein:
an element value of said phase rotating element is set to satisfy Fas 1 <Frp, where Fas 1 represents an antiresonance frequency of said first series interdigital transducer to which said phase rotating element is connected, and Frp represents a resonance frequency of said branch interdigital transducer.
18. A surface acoustic wave filter including one or more of the surface acoustic wave apparatus according to claim 17 .
19. A duplexer having a common terminal connected to an antenna, and a transmission filter and a reception filter connected to said common terminal, wherein:
one or both of said transmission filter and said reception filter includes the surface acoustic wave apparatus according to claim 17 .
20. The surface acoustic wave apparatus according to claim 13 , wherein:
said phase rotating element includes one or both of a transmission line and an inductance element.
21. A surface acoustic wave filter including one or more of the surface acoustic wave apparatus according to claim 20 .
22. A duplexer having a common terminal connected to an antenna, and a transmission filter and a reception filter connected to said common terminal, wherein:
one or both of said transmission filter and said reception filter include the surface acoustic wave apparatus according to claim 20 .
23. A surface acoustic wave filter including one or more of the surface acoustic wave apparatus according to claim 13 .
24. A duplexer having a common terminal connected to an antenna, and a transmission filter and a reception filter connected to said common terminal, wherein:
one or both of said transmission filter and said reception filter include the surface acoustic wave apparatus according to claim 13 .