Elastic wave resonator, elastic wave filter apparatus, and duplexer

Patent metadata

Field	Value
Publication number	US-2016156334-A1
Application number	US-201615014172-A
Country	US
Kind code	A1
Filing date	Feb 3, 2016
Priority date	Sep 6, 2013
Publication date	Jun 2, 2016
Grant date	—

Abstract

In an elastic wave resonator, a first IDT electrode, a second IDT electrode, a first reflector, and a second reflector are located on a piezoelectric substrate. The first IDT electrode and the second IDT electrode share a shared bus bar. Between a first terminal and a second terminal, the first IDT electrode and the second IDT electrode are connected in parallel. The shared bus bar and the first reflector are connected to the first terminal. A first bus bar and a second bus bar are connected to the second reflector, and are further connected to the second terminal.

First claim

What is claimed is:

1 . An elastic wave resonator comprising:
a first terminal; a second terminal; a piezoelectric substrate; a first IDT electrode and a second IDT electrode located on the piezoelectric substrate; and a first reflector and a second reflector, one of which is disposed on a first side of a region where the first IDT electrode and the second IDT electrode are located in an elastic wave propagation direction, the other one of which is disposed on a second side of the region in the elastic wave propagation direction, and which are shared by the first IDT electrode and the second IDT electrode; the first IDT electrode including a first bus bar and a shared bus bar disposed apart from the first bus bar; the second IDT electrode including the shared bus bar shared with the first IDT electrode and a second bus bar disposed apart from the shared bus bar; the first bus bar is disposed across the shared bus bar from the second bus bar; the shared bus bar is electrically connected to the first reflector and connected to the first terminal; the second reflector is electrically connected to the first bus bar and the second bus bar and is connected to the second terminal; the first IDT electrode and the second IDT electrode are electrically connected in parallel between the first terminal and the second terminal.

2 . The elastic wave resonator according to claim 1 , wherein a voltage application direction between the first bus bar and the shared bus bar in the first IDT electrode is the same as a projected polarization direction obtained by projecting a polarization direction of the piezoelectric substrate on a surface of the piezoelectric substrate, and a voltage application direction between the shared bus bar and the second bus bar in the second IDT electrode is opposite to the projected polarization direction.

3 . The elastic wave resonator according to claim 1 , wherein each of the first reflector and the second reflector includes a plurality of electrode fingers, a first end bus bar that couples first end portions of the electrode fingers, a second end bus bar that couples the second end portions of the electrode fingers, and an intermediate bus bar that couples intermediate portions of the electrode fingers.

4 . The elastic wave resonator according to claim 3 , wherein the first bus bar and the first end bus bar in the second reflector extend in the same direction and are integrated, and the second bus bar and the second end bus bar in the second reflector extend in the same direction and are integrated.

5 . The elastic wave resonator according to claim 3 , wherein the shared bus bar and the intermediate bus bar in the first reflector extend in the same direction and are integrated.

6 . The elastic wave resonator according to claim 1 , wherein the elastic wave filter is a one-port elastic wave resonator.

7 . An elastic wave filter apparatus comprising a plurality of elastic wave resonators, wherein at least one of the plurality of elastic wave resonators is the elastic wave resonator according to claim 1 .

8 . The elastic wave filter apparatus according to claim 7 , wherein the plurality of elastic wave resonators define a ladder circuit.

9 . The elastic wave filter apparatus according to claim 8 , wherein
the ladder circuit includes a plurality of series arm resonators and a plurality of parallel arm resonators; the series arm resonators and the parallel arm resonators are defined by the plurality of elastic wave resonators; and at least one of the series arm resonators and the parallel arm resonators is defined by the elastic wave resonator according to claim 1 .

10 . The elastic wave filter apparatus according to claim 7 , wherein a voltage application direction between the first bus bar and the shared bus bar in the first IDT electrode is the same as a projected polarization direction obtained by projecting a polarization direction of the piezoelectric substrate on a surface of the piezoelectric substrate, and a voltage application direction between the shared bus bar and the second bus bar in the second IDT electrode is opposite to the projected polarization direction.

11 . The elastic wave filter apparatus according to claim 7 , wherein each of the first reflector and the second reflector includes a plurality of electrode fingers, a first end bus bar that couples first end portions of the electrode fingers, a second end bus bar that couples the second end portions of the electrode fingers, and an intermediate bus bar that couples intermediate portions of the electrode fingers.

12 . The elastic wave filter apparatus according to claim 11 , wherein the first bus bar and the first end bus bar in the second reflector extend in the same direction and are integrated, and the second bus bar and the second end bus bar in the second reflector extend in the same direction and are integrated.

13 . The elastic wave filter apparatus according to claim 11 , wherein the shared bus bar and the intermediate bus bar in the first reflector extend in the same direction and are integrated.

14 . A duplexer comprising:
a first band-pass filter connected to an antenna terminal; and a second band-pass filter that is connected to the antenna terminal and has a pass band different from that of the first band-pass filter; wherein at least one of the first band-pass filter and the second band-pass filter includes the elastic wave resonator according to claim 1 .

15 . The duplexer according to claim 14 , wherein
at least one of the first band-pass filter and the second band-pass filter includes a plurality of elastic wave resonators; and at least one of the plurality of elastic wave resonators on a side nearest to the antenna terminal is the elastic wave resonator.

16 . The duplexer according to claim 14 , wherein a voltage application direction between the first bus bar and the shared bus bar in the first IDT electrode is the same as a projected polarization direction obtained by projecting a polarization direction of the piezoelectric substrate on a surface of the piezoelectric substrate, and a voltage application direction between the shared bus bar and the second bus bar in the second IDT electrode is opposite to the projected polarization direction.

17 . The duplexer according to claim 14 , wherein each of the first reflector and the second reflector includes a plurality of electrode fingers, a first end bus bar that couples first end portions of the electrode fingers, a second end bus bar that couples the second end portions of the electrode fingers, and an intermediate bus bar that couples intermediate portions of the electrode fingers.

18 . The duplexer according to claim 17 , wherein the first bus bar and the first end bus bar in the second reflector extend in the same direction and are integrated, and the second bus bar and the second end bus bar in the second reflector extend in the same direction and are integrated.

19 . The duplexer according to claim 17 , wherein the shared bus bar and the intermediate bus bar in the first reflector extend in the same direction and are integrated.

Assignees

• Murata Manufacturing Co

Inventors

• Nakagawa Ryo

Classifications

• H03H9/02992

  Details of bus bars, contact pads or other electrical connections for finger electrodes · CPC title

• H03H9/725 Primary

  Duplexers · CPC title

• H03H9/76

  Networks using surface acoustic waves · CPC title

• H03H9/6483

  Ladder SAW filters · CPC title

• H03H9/6476

  the tracks being electrically parallel · CPC title