Patent ID: 7679474
Filing Date: 2010-03-16
Classification: H03H

Abstract:
1. A surface acoustic wave resonator comprising: a piezoelectric substrate; an inter-digital transducer formed of two electrodes including a plurality of electrode fingers disposed on a surface of the piezoelectric substrate, the inter-digital transducer including a gradation region located at opposing ends thereof; and reflectors disposed near the opposing ends of the inter-digital transducer, wherein the gradation region includes electrode fingers of the plurality of electrode fingers, the electrode fingers included in the gradation region having an electrode finger pitch that gradually changes, wherein, at each opposing end of the inter-digital transducer and within the gradation region, the electrode finger pitch of 5 to 30 electrode fingers of the plurality of electrode fingers is different from the electrode finger pitch of electrode fingers of the plurality of electrode fingers located near a center of the inter-digital transducer, wherein the electrode finger pitch of electrode fingers of the plurality of electrode fingers located at a farthest end, which is one end of the gradation region and one of the opposing ends of the inter-digital transducer, is set to be 1% to 5% smaller than the electrode finger pitch of the electrode fingers located near the center of the inter-digital transducer, and wherein, within the gradation region, the electrode finger pitch is sequentially varied from the electrode finger pitch of an electrode finger of the plurality of electrode fingers located at the farthest end to gradually approach the electrode finger pitch of the electrode fingers located near the center of the inter-digital transducer, and is sequentially varied from the electrode finger pitch of an electrode finger of the plurality of electrode fingers located at an end of the inter-digital transducer that is opposite from the farthest end to gradually approach the electrode finger pitch of the electrode fingers located near the center of the inter-digital transducer.