Surface acoustic wave resonator, surface acoustic wave device, and communications equipment

• US 20070024397A1
• Filed: 05/25/2006
• Published: 02/01/2007
• Est. Priority Date: 05/27/2005
• Status: Active Grant

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Corporation
• Inventors: Tanaka, Hiroyuki, Nakai, Tsuyoshi, Iioka, Kiyohiro, Makibuchi, Daisuke, Otsuka, Kazuhiro, Fukuura, Atsuomi, Obara, Ikuo
• Granted Patent: US 7,504,911 B2
• Time in Patent Office: Days
• US Class Current: 333/195
• CPC Class Codes: H03H 9/14576 Transducers whereby only the last fingers have different characteristics with respect to the other fingers, e.g. different shape, thickness or material, split finger
• CPC Class Codes: H03H 9/14582 the last fingers having a different pitch
• CPC Class Codes: H03H 9/14588 Horizontally-split transducers
• CPC Class Codes: H03H 9/6469 via two connecting electrodes

Abstract

A plurality of IDT electrodes 2 to 7 each having a large number of electrode fingers extending in a direction perpendicular to a propagation direction of a surface acoustic wave propagating on a piezoelectric substrate 1 are arranged on the piezoelectric substrate 1 along the propagation direction, and each of the two adjacent IDT electrodes out of the plurality of IDT electrodes 2 to 7 comprises a variable pitch section and a fixed pitch section. The electrode finger pitch in the variable pitch section gradually decreases toward the boundary between the two adjacent IDT electrodes, and the minimum electrode finger pitch portion in the two variable pitch sections is on one side spaced apart from the boundary. There can be provided a surface acoustic wave apparatus having a large pass bandwidth, having a low insertion loss, and having improved flatness in a pass band.

Claims

1. A surface acoustic wave resonator comprising a plurality of IDT electrodes arranged on a piezoelectric substrate along a propagation direction of a surface acoustic wave propagating on the piezoelectric substrate and each having a number of electrode fingers extending in a direction perpendicular to the propagation direction, wherein

two adjacent IDT electrodes out of the plurality of IDT electrodes comprises a variable pitch section, that is a section in close proximity to an end of the other IDT electrode, where an electrode finger pitch is variable, and a fixed pitch section, where the electrode finger pitch is fixed,

the electrode finger pitch in the variable pitch section basically decreases toward the boundary between the two adjacent IDT electrodes, and

the minimum electrode finger pitch portion in the two adjacent variable pitch sections is on one side spaced apart from the boundary.

2. The surface acoustic wave resonator according to claim 1, wherein

the average electrode finger pitch in the variable pitch section is made shorter than the electrode finger pitch in the fixed pitch section.

3. The surface acoustic wave resonator according to claim 1, wherein

the electrode finger pitch in the fixed pitch section in one of the two adjacent IDT electrodes is longer than the electrode finger pitch in the fixed pitch section in the other IDT electrode, and

the minimum electrode finger pitch portion in the variable pitch sections is on the side of the one ID electrode.

4. The surface acoustic wave resonator according to claim 1, wherein

the electrode finger pitch in the fixed pitch section in one of the two adjacent IDT electrodes is longer than the electrode finger pitch in the fixed pitch section in the other IDT electrode, and

the average electrode finger pitch in the variable pitch section in the one IDT electrode is shorter than the average electrode finger pitch in the variable pitch section in the other IDT electrode.

5. The surface acoustic wave resonator according to claim 1, wherein

a plurality of minimal electrode finger pitch portions exist in the two adjacent variable pitch sections.

6. The surface acoustic wave resonator according to claim 5, wherein

the minimum one of the plurality of minimal electrode finger pitch portions is on one side spaced apart from the boundary between the two adjacent IDT electrodes.

7. The surface acoustic wave resonator according to claim 1, wherein

at least one of the two adjacent variable pitch sections comprises a wide pitch region having an electrode finger pitch wider than the electrode finger pitch in the fixed pitch section.

8. The surface acoustic wave resonator according to claim 7, wherein

the wide pitch region is in an area, on the side of the boundary between the variable pitch section and the fixed pitch section, of the variable pitch section.

9. A surface acoustic wave apparatus having the surface acoustic wave resonator according to claim 1, and an input/output terminal connected to the surface acoustic wave resonator.

10. A surface acoustic wave apparatus, wherein

a surface acoustic wave resonator for generating one or more mode resonances is connected to the surface acoustic wave resonator according to claim 1.

11. A surface acoustic wave apparatus in which the surface acoustic wave resonators according to claim 1 are two-stage cascade-connected.

12. Communications equipment comprising at least one of a receiving circuit and a transmission circuit, wherein the surface acoustic wave resonator according to claim 1 is carried thereon.