| 摘要 |
PURPOSE: An end-surface reflection type surface acoustic wave filter is provided to increase attenuation amount outside a pass band while insertion loss characteristics are not seriously deteriorated. CONSTITUTION: A filter is a longitudinally coupled resonator type surface acoustic wave filter using an SH type surface acoustic wave, which has the first and second grooves(2b,2c) formed in a piezoelectric substrate(2) at the top surface(2a) thereof so as to be substantially parallel to each other and spaced apart from each other by a predetermined distance. In addition, IDTs(5,6) which are provided between the grooves for defining the longitudinally coupled resonator type surface acoustic wave filter, reflection end-surfaces disposed on side surfaces of the first and the second grooves at the IDT sides, and one of a resin-coating layer and a protective layer made of SiO2, are provided on the top surface of the piezoelectric substrate.
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