Tdk Corporation

Michiyuki Nakazawa

Seisuke Mochizuka

Masaki Takahashi

Masahiro Nakano

Katsuo Sato

Noritoshi Kimura

Disclosed is a surface acoustic wave filter comprising two or more IDTs arranged in a propagation direction of the surface acoustic wave, wherein said two or more IDTs include at least one pair of IDTs arranged adjacent to each other in order to be acoustically coupled to each other, and have different numbers of paired electrode fingers, and a pitch between each neighboring two of almost all of the electrode fingers included in one of the pair of IDTs which has the smaller number of paired electrode fingers is made different from one to another in order that the IDTs should include no primary pitch area.

Longitudinally coupled resonator-type surface acoustic wave filter

A SAW filter comprises an IDT disposed on a piezo-electric substrate, wherein the IDT includes comb-shaped electrodes having a plurality of interdigital electrodes arranged in a propagation direction of surface acoustic waves and bus bars for connecting these interdigital electrodes, arranged in opposition, and the interdigital electrodes are crossed with one another. The IDT comprises one or more branch electrodes branched from the interdigital electrode and positioned in a non-overlap zone between an overlap zone at which the interdigital electrodes overlap and the bus bar, and the branch electrode includes a branch electrode body extending in a direction substantially orthogonal to the propagation direction of surface acoustic wave. The SAW filter can be applied to any of a longitudinally coupled multi-mode filter, a ladder type filter, a resonator, a filter having a resonator connected in series to a longitudinally coupled multi-mode filter, and the like. A SAW filter and a SAW resonator highly resistant to damages to the electrodes with high Q and low insertion loss can be provided.

Surface acoustic wave filter and resonator utilizing a branch electrode with an electrically opened end

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, &#x3bb;a&#x2267;&#x3bb;b is established, where &#x3bb;a represents an electrode finger pitch of the IDT to which the phase rotating element is connected, and &#x3bb;b represents an electrode finger pitch of the IDT to which no phase rotating element is connected.

Surface acoustic wave apparatus

A surface acoustic wave device includes a piezoelectric substrate having Al or Al alloy electrodes formed on a surface of the substrate, a metal oxide film provided on the substrate and the electrodes. The metal oxide film is formed by a process including depositing a metal thin film having a thickness sufficiently thin so that the deposited metal thin film is discontinuous including voids, and oxidizing the discontinuous metal thin film, and the metal oxide film includes a continuous portion without voids covering the electrodes.

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Tokyo, Japan

Michiyuki Nakazawa