Patent ID: 7075390

Claim:
A surface acoustic wave device comprising: a surface acoustic wave transducer including a positive electrode finger, a negative electrode finger, and a floating electrode arranged between the positive and negative electrode fingers, which are formed on a langasite single crystal substrate, in which a substrate orientation and a surface acoustic wave propagation direction are selected to have a natural unidirectional property, wherein the positive and negative electrode fingers and the floating electrode are formed along the propagation direction of the surface acoustic wave to reverse the national unidirectional property, wherein the langasite single crystal substrate is in a range âˆ’5Â°â‰¦Ï†â‰¦50Â°, 13Â°â‰¦Î¸â‰¦14Â°, and 20Â°â‰¦Ïˆâ‰¦30Â°, or is the equivalent orientation in crystallography, when the substrate orientation and the surface acoustic wave propagation direction are described in (Ï†,Î¸,Ïˆ) by Euler-angles viewing and wherein a width of the positive and negative electrode fingers is about Î»/8, a distance between each center of the positive and negative electrode fingers is about 6/8Î», a distance g between each center of the positive electrode finger and the floating electrode is 13/40Î»â‰¦gâ‰¦14/40Î», and a width W of the floating electrode is 11/40Î»â‰¦Wâ‰¦13/40Î», when Î» is a wavelength of the surface acoustic wave.