US 7,679,474 B2 · Surface acoustic wave resonator, and surface acoustic wave filter

Abstract

A surface acoustic wave resonator has a piezoelectric substrate (11), an IDT (13) formed of a plurality of electrode fingers (12) disposed on piezoelectric substrate (11), and reflectors (14) disposed near the opposite ends of IDT (13). The IDT (13) has a gradation region where the electrode finger pitch of the plurality of electrode fingers (12) at the opposite ends is different from the electrode finger pitch near the center of the IDT (13). In this gradation region, the electrode finger pitches are sequentially varied in the range from the electrode finger at the farthest end that is one end of the gradation region to the electrode finger lying at the other end of the gradation region. The electrode finger pitch of the electrode fingers at the farthest end that is one end of the gradation region is set to be 1 through 5% smaller than the electrode finger pitch near the center of the IDT (13).

Drawings

Drawings are temporarily unavailable. Open the PDF at USPTO

Drawings

Claims6

Dependent claims

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.

5 more elements

A surface acoustic wave filter comprising:

a piezoelectric substrate;
a plurality of inter-digital transducers disposed closely on an identical surface acoustic wave propagation path on the piezoelectric substrate;
and
reflectors disposed on opposite ends of a structure including the plurality of inter-digital transducers,
wherein at least one of the plurality of inter-digital transducers is a first inter-digital transducer connected to a signal path in series, and at least one of the plurality of inter-digital transducers is a second inter-digital transducer connected between the signal path and a ground,
wherein the first inter-digital transducer is formed of two electrodes including a plurality of electrode fingers, and the first inter-digital transducer includes-has a gradation region located at opposing ends thereof,
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 first 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 first 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 first 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 first 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 first 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 first 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 first inter-digital transducer.

7 more elements

Dependencies are inferred from the claim text.

Description5,431 words

Summary1,451 words

#1. Field of the Invention

#The present invention relates to a surface acoustic wave resonator and surface acoustic wave filter for use in a portable phone.

#2. Description of the Related Art

Brief description of the drawings17 figures

#FIG. 1 is a plan view of a surface acoustic wave resonator in accordance with a first exemplary embodiment of the present invention.

#FIG. 2 is an enlarged view of the left end of an IDT shown in FIG. 1.

#FIG. 3 is a diagram showing a simulation result of the reflection characteristic of the resonator of practical example 1, in the surface acoustic wave resonator of the first exemplary embodiment.

Detailed description3,359 words

#Embodiments of the present invention are described in detail hereinafter with reference to the accompanying drawings. The same elements are denoted with the same reference marks, and the descriptions of those elements are omitted. The following drawings are schematic, and do not accurately represent the number of electrode fingers and a pitch.

#FIG. 1 is a plan view of surface acoustic wave resonator 10 in accordance with a first exemplary embodiment of the present invention. Surface acoustic wave resonator 10 has the following elements:

#IDT 13 including a plurality of electrode fingers 12 formed on the surface of piezoelectric substrate 11 made of 39° Y cut X propagation lithium tantalate (LiTaO3); and

Facts

Application

10/580,915Filed 6 Jan 2005

Priority

JP 2004-0038609 Jan 2004

Published

US 2009/0108960 A130 Apr 2009

Granted

16 Mar 2010

Term ends

5 Aug 2027

Estimated · how

20 years from earliest known nonprovisional domestic filing plus recorded patent term adjustment, including 941 days of adjustment. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification4 codes

H03H 9/14544
For networks using surface acoustic waves: transducers of particular shape or position
H03H 9/14582
Transducers whereby only the last fingers have different characteristics with respect to the other fingers, e.g. different shape, thickness or…:…
H03H 9/6483
Coupled resonator filters: ladder SAW filters
H03H
Impedance networks

Timeline

9 Jan 2004Priority claimedJP 2004-003860
6 Jan 2005Application filedUS 10/580,915
15 May 2008Assigned to Matsushita Electric Industrial Co., Ltd.assignment of assignor's interest
11 Nov 2008Assigned to Panasonic Corporationchange of name
30 Apr 2009PublishedUS 2009/0108960 A1
16 Mar 2010GrantedUS 7,679,474 B2
14 May 2015Assigned to Skyworks Panasonic Filter Solutions Japan Co., Ltd.assignment and acknowledgment
16 Sep 2016Assigned to Skyworks Filter Solutions Japan Co., Ltd.change of name
12 Oct 2026TodayWithin its term
5 Aug 2027Term endsEstimated, includes 941 days of adjustment

Surface acoustic wave resonator, and surface acoustic wave filter

Life of this patent

Surface acoustic wave resonator, and surface acoustic wave filter

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims6

Description5,431 words

Drawings

Classification4 codes

Life of this patent

Description5,431 words