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AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsHiroyuki Nakamura, Toru Yamada, Kazunori Nishimura, Toshio Ishizaki
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Disclosed is a surface acoustic wave filter on a piezoelectric substrate. The filter includes at least two surface acoustic wave resonators that each has a reflector electrode on both sides of an IDT electrode as an inter-digital transducer electrode. At least two of the resonators are disposed on a piezoelectric substrate in positions near each other so that the propagation direction of surface acoustic waves are in parallel to make an acoustic coupling. In an embodiment, the acoustic coupling is a direct coupling. The IDT electrode has a plurality of electrode fingers connected so as not to cancel respective electric charges. The IDT electrode is constituted by at least three divisional IDT electrodes. A pair of the electrode fingers can have a reverse phase relation with respect to each other. Also, in a multi-stage surface acoustic wave filter, the electrode fingers can be included in an upper IDT electrode of a top stage of the filter, and in a lower IDT electrode of a bottom stage of such filter.
A surface acoustic wave filter on a piezoelectric substrate comprising at least two surface acoustic wave resonators each having a reflector electrode on both sides of an IDT electrode as an inter-digital transducer electrode, at least two of said resonators being disposed on a piezoelectric substrate in positions nearby one another in which directions of propagation of the respective surface acoustic waves are parallel with one another to make an acoustic coupling, wherein plural electrode fingers are included in at least one IDT electrode, wherein at least a pair of adjacent electrode fingers are in reverse phase relations to each other, wherein said plural electrode fingers are connected so as not to cancel respective electric charges and, wherein said at least one IDT electrode is constituted by three or more divisional IDT electrodes.
A multi-stage surface acoustic wave filter on a piezoelectric substrate comprising a plurality of stages of surface acoustic wave filters vertically connected by an inter-stage connecting electrode pattern, said surface acoustic filter having two surface acoustic wave resonators each having a reflector electrode on both sides of an IDT electrode, said resonators being disposed in positions nearby one another in which directions of propagation of the respective surface acoustic waves are parallel with one another to make an acoustic coupling,
A surface acoustic wave filter on a piezoelectric substrate comprising at least two surface acoustic wave resonators each having a reflector electrode on both sides of an IDT electrode as an inter-digital transducer electrode, at least two of said resonators being disposed on a piezoelectric substrate in positions nearby one another in which directions of propagation of the respective surface acoustic waves are parallel with one another to make a direct acoustic coupling, wherein said IDT electrode which has a plurality of electrode fingers is constituted by at least three divisional IDT electrodes, and said plural electrode fingers are connected so as not to cancel respective electric charges.
Dependencies are inferred from the claim text.