Patent ID: 8736140

Claim:
A surface acoustic wave resonator, comprising: a piezoelectric substrate; an interdigital transducer (IDT) that includes electrode fingers configured to excite 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; and reflectors that include a plurality of electrode fingers and that are on the both sides of the IDT, wherein 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 of 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 region 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, 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, and wherein an electrode finger interval of the reflectors is greater than the electrode finger intervals of the first, second, and third regions.