Surface acoustic wave filter device having a signal line connected by a wire to a floating electrode

#The present application claims priority under 35 U.S.C. § 119 to Japanese Application No. 076584/2000 filed on Mar. 17, 2000, which is hereby incorporated by reference in its entirety for all purposes.

#1. Field of the Invention

#The present invention relates to a surface acoustic wave filter device utilizing surface acoustic waves.

#FIG. 1 shows a schematic diagram of a SAW filter device of a first preferred embodiment of the present invention.

#FIG. 2 shows a plane view of a SAW filter of the first preferred embodiment of the present invention.

#FIG. 3 shows a plane view of a ceramic package of the first preferred embodiment of the present invention.

#The preferred embodiments are described below with respect the accompanying drawings. The same reference numerals are applied to the same elements in each embodiment and drawings.

#FIG. 1 is a schematic diagram of a Surface Acoustic Wave (SAW) filter device of a first preferred embodiment. The SAW filter device 11 has a SAW filter 12, which is formed on a piezoelectric substrate, and a multi-layer ceramic package. The SAW filter 12 has a series arm 13, a first parallel arm 14 and a second parallel arm 15. The first parallel arm 13 is disposed between a filter input terminal TFi and a filter output terminal TFo, and the first parallel arm 14 and the second parallel arm 15 are disposed between the series arm 13 and a parallel arm reference potential terminal TPg.

#The series arm 13 has a first series resonator S1, a second series resonator S2, and a third series resonator S3. These resonators are disposed in series between the filter input terminal TFi and the filter output terminal TFo. One terminal of the first series resonator S1 is connected to the filter input terminal TFi, and another terminal of the first series resonator S1 is connected to a node n1. One terminal of the second series resonator S2 is connected to the node n1, and another terminal of the second series resonator S2 is connected to a node n2. One terminal of the third series resonator S3 is connected to the node n2, and another terminal of the third series resonator S3 is connected to the filter output terminal TFo.