Patent ID: 8084917
Filing Date: 2011-12-27
Classification: H03H

Abstract:
1. A surface acoustic wave resonator, comprising: a piezoelectric substrate; and an interdigital transducer (IDT) that includes electrode fingers exciting a surface acoustic wave on the piezoelectric substrate, a first region at a center of the IDT, and a second region and a third region at opposite sides of the IDT, wherein in the IDT, a line occupation rate at which an electromechanical coupling coefficient becomes a maximum is different from the line occupation rate at which reflection of the surface acoustic wave becomes a maximum, wherein each of the first, second, and third regions has a uniform electrode finger interval, and the electrode finger intervals in the second and third regions are larger than the electrode finger interval of the first region, wherein the first region has a first line occupation rate, the second region has a second line occupation rate, and the third regions has a third line occupation rate, and the first, second and third line occupation rates are uniform in the first, second, and third regions respectively, and an electromechanical coupling coefficient at the first line occupation rate is larger than the electromechanical coupling coefficients at the second line occupation rate and the third line occupation rate, and the reflection of the surface acoustic wave at the second line occupation rate and the third line occupation rate is larger than the reflection of the surface acoustic wave at the first line occupation rate, and wherein the line occupation rate is defined as a value obtained by dividing a width of the electrode finger by an electrode finger interval that is an interval between centers of the adjacent electrode fingers.