Patent ID: 7812688
Filing Date: 2010-10-12
Classification: H03H

Abstract:
1. A surface acoustic wave filter comprising: a piezoelectric substrate made of lithium niobate; a series resonator including a first interdigital transducer electrode provided on the piezoelectric substrate; a parallel resonator including a second interdigital transducer electrode provided on the piezoelectric substrate, the parallel resonator being electrically connected to the series resonator; and a dielectric layer covering at least one of the first interdigital transducer electrode or the second interdigital transducer electrode, wherein the series resonator has a first excitation region which includes a first electrode facing region and a first non-electrode facing region; the parallel resonator has a second excitation region which includes a second electrode facing region and a second non-electrode facing region; a first apodized weighting factor which is a ratio of an area of the first non-electrode facing region to an area of the first excitation region is smaller than a second apodized weighting factor which is a ratio of an area of the second non-electrode facing region to an area of the second excitation region; and the piezoelectric substrate is made of −30° to +30° rotated Y-cut lithium niobate.