Patent ID: 6667673
Filing Date: 2003-12-23
Classification: H03H

Abstract:
A dualmode surface acoustic wave filter comprising:an input terminal and an output terminal, at least one of the input terminal and the output terminal being balanced; a first filter track and a second filter track, each track comprising: at least one first transducer comprising an even-numbered plurality of transducer fingers electrically connected to a respective busbar and arranged interdigitally; a plurality of second transducers, each second transducer comprising an even-numbered plurality of transducer fingers electrically connected to a respective busbar and arranged interdigitally; and reflector structures; wherein: the second transducers serve as coupling transducers, the second transducers of the first filter track being electrically connected to respective second transducers of the second filter track, and the at least one first transducer of the first track serving as an input transducer; the at least one first transducer of the second filter track serving as an output transducer; at least one balanced terminal chosen from the input and output terminal being electrically connected to the busbars of the respective input and output transducer; in each filter track, a finger arrangement of the first transducer being point-symmetrical with respect to a center of the respective transducer; in each filter track, the at least one first transducer being arranged between two respective second transducers; in a respective track, a finger arrangement of the two second transducers being point-symmetrical to one another with respect to a center of the corresponding first transducer; or in a respective track, a finger arrangement of the two second transducers being mirror-symmetrical to one another with respect to an axis that is orthogonal to a wave propagation direction, which axis passes through the center of the corresponding first transducer.