Surface acoustic wave (SAW) resonator, SAW filter and SAW antenna duplexer using the SAW resonator
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsHiroyuki Nakamura, Shunichi Seki, Kazunori Nishimura, Toru Sakuragawa
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Abstract
A SAW resonator includes an IDT electrode formed on a piezoelectric substrate and reflector electrodes disposed on both sides of the IDT electrode. The IDT electrode includes first finger-electrodes, second finger-electrodes and strip-line electrodes. The first and the second finger-electrodes do not overlap with each other but are acoustically coupled together by the strip-line electrodes. This acoustic coupling by the strip-line electrodes eliminates the need for a common bus-bar electrode, so that the loss caused by the resistance of the common bus-bar electrode can be reduced, and the SAW resonator can be downsized.
Claims12
A surface acoustic wave (SAW) resonator comprising:
- a piezoelectric substrate:
- an interdigital transducer (IDT) electrode formed on said piezoelectric substrate;
- and
- a reflector electrode disposed adjacent to said IDT electrode;
- wherein said IDT electrode comprises:
- a plurality of first finger-electrodes;
- a plurality of second finger-electrodes;
- a plurality of strip-line electrodes;
- a first bus-bar electrode coupled to said first finger-electrodes;
- and
- a second bus-bar electrode coupled to said second finger-electrodes;
- wherein said first finger-electrodes and said second finger-electrodes do not overlap with each other, but are acoustically coupled together by said strip-line electrodes,
- wherein said strip-line electrodes overlap with at least one of said first finger-electrodes and said second finger-electrodes,
- wherein said IDT electrode and said reflector electrode form at least two resonating units,
- wherein said at least two resonating units are coupled in series via said strip-line electrodes,
- wherein said IDT electrode further comprises a plurality of dummy electrodes respectively disposed between said first finger-electrodes and said second finger-electrodes such that each of said dummy electrodes faces a respective one of said strip-line electrodes, and
- wherein each of said dummy electrodes has a width greater than that of each of said first finger-electrodes and that of each of said second finger-electrodes.
A surface acoustic wave (SAW) filter comprising:
- a piezoelectric substrate;
- a plurality of interdigital transducer (IDT) electrodes disposed on said piezoelectric substrate adjacent to each other along a propagating direction of the SAW;
- a first reflector electrode disposed at a first side of said plurality of IDT electrodes;
- and
- a second reflector electrode disposed at a second side of said plurality of IDT electrodes,
- wherein at least one of said IDT electrodes includes a first finger-electrode, a second finger-electrode and a strip-line electrode, and
- wherein said first finger-electrode and said second finger-electrode do not overlap with each other but are acoustically coupled together by said strip-line electrode.
Dependencies are inferred from the claim text.