# US 12,184,267 B2 · Surface acoustic wave resonator, acoustic wave filter, and multiplexer

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- Number: US 12,184,267 B2
- Document ID: US12184267B2
- Status: Granted
- Kind: B2
- Application number: 17/844,986
- Filed: 2022-06-21
- Published: 2022-12-29
- Granted: 2024-12-31
- Earliest claimed: 2021-06-23
- Assignees: Murata Manufacturing Co., Ltd.
- Applicants: Murata Manufacturing Co., Ltd.
- Inventors: Akira Noguchi
- Web page: https://patentgrep.com/patent/US12184267B2

## CPC

- H03H 9/25: Constructional features of resonators using surface acoustic waves {(devices for manipulating acoustic surface waves in general G10K11/36)}
- H03H 9/02637: {Details concerning reflective or coupling arrays}
- H03H 9/14541: {Multilayer finger or busbar electrode}
- H03H 9/14582: {the last fingers having a different pitch}
- H03H 9/6483: {Ladder SAW filters}
- H03H 9/725: {Duplexers}
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)

## Abstract

A surface acoustic wave resonator includes one IDT electrode and reflectors. When a distance between an electrode finger Fe(k) and an electrode finger Fe(k+1) is defined as a k-th electrode finger pitch, in an electrode finger Fe(k−1), the electrode finger Fe(k), and the electrode finger Fe(k+1), a value obtained by dividing a difference between the electrode finger pitch and a section average electrode finger pitch, which is an average of the electrode finger pitch and the electrode finger pitch, by an overall average electrode finger pitch is defined as a pitch deviation ratio, and a distribution obtained by calculating the pitch deviation ratio for all electrode fingers of the IDT electrode or the reflectors is defined as a histogram of the pitch deviation ratio, the IDT electrode or the reflectors have a standard deviation of the pitch deviation ratio in the histogram larger than or equal to about 0.2%.

## Claims

### Claim 1

A surface acoustic wave resonator comprising:
a substrate having piezoelectricity;
an IDT electrode on the substrate; and
reflectors sandwiching the IDT electrode in a propagation direction of an acoustic wave; wherein
the IDT electrode is defined by only one IDT electrode;
the IDT electrode and the reflectors each include a plurality of electrode fingers extending in a direction crossing the propagation direction of the acoustic wave and being in parallel or substantially in parallel to one another; and
when
a distance between a k-th electrode finger and a (k+1)-th electrode finger in the propagation direction of the acoustic wave is defined as a k-th electrode finger pitch, where k is an integer larger than or equal to 2;
in a (k−1)-th electrode finger, the k-th electrode finger, and the (k+1)-th electrode finger adjacent to each other, a value obtained by dividing a difference between the k-th electrode finger pitch and a section average electrode finger pitch, which is an average of the (k−1)-th electrode finger pitch and the (k+1)-th electrode finger pitch, by an overall average electrode finger pitch, which is an average pitch of overall electrode fingers which the IDT electrode or the reflectors have, the IDT electrode or the reflectors including the adjacent three electrode fingers, is defined as a pitch deviation ratio of the k-th electrode finger; and
a distribution of the pitch deviation ratio obtained by calculating the pitch deviation ratio of the k-th electrode finger for all of the electrode fingers which the IDT electrode or the reflectors include, the IDT electrode or the reflectors including the adjacent three electrode fingers, is defined as a histogram of the pitch deviation ratio;
at least one of the IDT electrode and the reflectors has a standard deviation of the pitch deviation ratio in the histogram larger than or equal to about 0.2%.

### Claim 2 (depends on 1)

The surface acoustic wave resonator according to claim 1, wherein the surface acoustic wave resonator has a relationship in which, when the electrode finger pitches of four of the plurality of electrode fingers adjacent to one another in the propagation direction of the acoustic wave are denoted as P(k−1), P(k), and P(k+1) in order of alignment in the propagation direction of the acoustic wave, P(k−1)<P(k+1)<P(k) or P(k−1)>P(k+1)>P(k) is at least partially satisfied.

### Claim 3 (depends on 2)

The surface acoustic wave resonator according to claim 2, wherein
a portion of the electrode fingers of the plurality of electrode fingers has a constant or substantially constant electrode finger pitch; and
electrode fingers that remain except the portion have a relationship of P(k−1)<P(k+1)<P(k) or P(k−1)>P(k+1)>P(k).

### Claim 4 (depends on 3)

The surface acoustic wave resonator according to claim 3, wherein
the plurality of electrode fingers included in the IDT electrode have a constant or substantially constant electrode finger pitch; and
the plurality of electrode fingers included in the reflectors have a relationship of P(k−1)<P(k+1)<P(k) or P(k−1)>P(k+1)>P(k).

### Claim 5 (depends on 3)

The surface acoustic wave resonator according to claim 3, wherein
the plurality of electrode fingers included in the reflectors have a constant or substantially constant electrode finger pitch; and
the plurality of electrode fingers included in the IDT electrode have a relationship of P(k−1)<P(k+1)<P(k) or P(k−1)>P(k+1)>P(k).

### Claim 6

A surface acoustic wave resonator comprising:
a substrate having piezoelectricity; and
an IDT electrode on the substrate; wherein
the IDT electrode is defined by only one IDT electrode;
the IDT electrode includes a plurality of electrode fingers extending in a direction crossing a propagation direction of an acoustic wave and being in parallel or substantially in parallel to one another; and
when
a distance between a k-th electrode finger and a (k+1)-th electrode finger in the propagation direction of the acoustic wave is defined as a k-th electrode finger pitch, where k is an integer larger than or equal to 2;
in a (k−1)-th electrode finger, the k-th electrode finger, and the (k+1)-th electrode finger adjacent to each other, a value obtained by dividing a difference between the k-th electrode finger pitch and a section average electrode finger pitch, which is an average of the (k−1)-th electrode finger pitch and the (k+1)-th electrode finger pitch, by an overall average electrode finger pitch, which is an average pitch of overall electrode fingers which the IDT electrode including the adjacent three electrode fingers has, is defined as a pitch deviation ratio of the k-th electrode finger; and
a distribution of the pitch deviation ratio obtained by calculating the pitch deviation ratio of the k-th electrode finger for all of the electrode fingers which the IDT electrode including the adjacent three electrode fingers includes is defined as a histogram of the pitch deviation ratio;
the IDT electrode has a standard deviation of the pitch deviation ratio in the histogram larger than or equal to about 0.2%.

### Claim 7 (depends on 6)

The surface acoustic wave resonator according to claim 6, wherein
the surface acoustic wave resonator has a relationship in which, when the electrode finger pitches of four electrode fingers adjacent to one another in the propagation direction of the acoustic wave are denoted as P(k−1), P(k), and P(k+1) in order of alignment in the propagation direction of the acoustic wave, P(k−1)<P(k+1)<P(k) or P(k−1)>P(k+1)>P(k) is at least partially satisfied.

### Claim 8 (depends on 7)

The surface acoustic wave resonator according to claim 7, wherein
a portion of the electrode fingers of the plurality of electrode fingers has an electrode finger pitch that is constant or substantially constant; and
electrode fingers that remain except the portion have a relationship of P(k−1)<P(k+1)<P(k) or P(k−1)>P(k+1)>P(k).

### Claim 9 (depends on 1)

The surface acoustic wave resonator according to claim 1, wherein all of the electrode finger pitches between two electrode fingers adjacent to each other in the propagation direction of the acoustic wave are varied with one another.

### Claim 10 (depends on 1)

An acoustic wave filter comprising:
the surface acoustic wave resonator according to claim 1.

### Claim 11 (depends on 10)

The acoustic wave filter according to claim 10, wherein
the acoustic wave filter includes a ladder circuit including series-arm resonators and parallel-arm resonators; and
at least one of the parallel-arm resonators is defined by the surface acoustic wave resonator.

### Claim 12 (depends on 10)

The acoustic wave filter according to claim 10, wherein the surface acoustic wave resonator has a relationship in which, when the electrode finger pitches of four of the plurality of electrode fingers adjacent to one another in the propagation direction of the acoustic wave are denoted as P(k−1), P(k), and P(k+1) in order of alignment in the propagation direction of the acoustic wave, P(k−1)<P(k+1)<P(k) or P(k−1)>P(k+1)>P(k) is at least partially satisfied.

### Claim 13 (depends on 12)

The acoustic wave filter according to claim 12, wherein
a portion of the electrode fingers of the plurality of electrode fingers has a constant or substantially constant electrode finger pitch; and
electrode fingers that remain except the portion have a relationship of P(k−1)<P(k+1)<P(k) or P(k−1)>P(k+1)>P(k).

### Claim 14 (depends on 13)

The acoustic wave filter according to claim 13, wherein
the plurality of electrode fingers included in the IDT electrode have a constant or substantially constant electrode finger pitch; and
the plurality of electrode fingers included in the reflectors have a relationship of P(k−1)<P(k+1)<P(k) or P(k−1)>P(k+1)>P(k).

### Claim 15 (depends on 13)

The acoustic wave filter according to claim 13, wherein
the plurality of electrode fingers included in the reflectors have a constant or substantially constant electrode finger pitch; and
the plurality of electrode fingers included in the IDT electrode have a relationship of P(k−1)<P(k+1)<P(k) or P(k−1)>P(k+1)>P(k).

### Claim 16 (depends on 10)

A multiplexer comprising:
a transmission filter; and
a reception filter; wherein
the transmission filter includes the acoustic wave filter according to claim 10.

### Claim 17 (depends on 6)

An acoustic wave filter comprising:
the surface acoustic wave resonator according to claim 6.

### Claim 18 (depends on 17)

The acoustic wave filter according to claim 17, wherein
the acoustic wave filter includes a ladder circuit including series-arm resonators and parallel-arm resonators; and
at least one of the parallel-arm resonators is defined by the surface acoustic wave resonator.

### Claim 19 (depends on 17)

The acoustic wave filter according to claim 17, wherein
the surface acoustic wave resonator has a relationship in which, when the electrode finger pitches of four electrode fingers adjacent to one another in the propagation direction of the acoustic wave are denoted as P(k−1), P(k), and P(k+1) in order of alignment in the propagation direction of the acoustic wave, P(k−1)<P(k+1)<P(k) or P(k−1)>P(k+1)>P(k) is at least partially satisfied.

### Claim 20 (depends on 17)

A multiplexer comprising:
a transmission filter; and
a reception filter; wherein
the transmission filter includes the acoustic wave filter according to claim 17.