| 摘要 |
PROBLEM TO BE SOLVED: To reduce the loss as a SAW filter by arranging short-circuit type gratings outside both an open type grating and a grating opening on a piezoelectric substrate, having a recessed surface as the opposite speed surface in the main propagation direction of a surface acoustic wave, in the propagation direction of the surface wave. SOLUTION: On the piezoelectric substrate of 360 deg. LiTaO3, an area A inside a waveguide is formed by arranging an open type inside grating 2 along the propagation direction of the surface wave. At right angles to the propagation direction of the surface wave, outside gratings (electrode finger array) 3a and 3b are arranged on both the sides of the inside grating (electrode finger array) 2 in parallel to and at the same pitch with the inside grating 2. The outsides of the outside gratings 3a and 3b are connected by bus bars 4a and 4b to form an area B for a short-circuit type grating. The open type inside grating 2 is always faster in phase speed than the short-circuit type outside gratings 3a and 3b.
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