Multiplexer, radio-frequency front-end circuit, and communication apparatus

Patent metadata

Field	Value
Publication number	US-2019123720-A1
Application number	US-201816218531-A
Country	US
Kind code	A1
Filing date	Dec 13, 2018
Priority date	Jun 29, 2016
Publication date	Apr 25, 2019
Grant date	—

Abstract

A quadplexer includes a first filter and a second filter whose passband has frequencies higher than the first filter. The first filter has a ladder filter structure including series resonators disposed on a first path and parallel resonators disposed on a path connecting the first path and ground. A series resonator that is closest to a common terminal among the series resonators includes an IDT electrode that excites elastic waves, and a reflector that reflects the elastic waves excited by the IDT electrode. A distance between the IDT electrode and the reflector is greater than or equal to about 0.44λ and less than about 0.5λ where λ is a wavelength of the elastic waves that is defined by an electrode cycle of the IDT electrode.

First claim

What is claimed is:

1 . A multiplexer comprising:
a common terminal; a first terminal and a second terminal; a first filter disposed on a first path connecting the common terminal and the first terminal; and a second filter disposed on a second path connecting the common terminal and the second terminal, the second filter having a passband with frequencies higher than a passband of the first filter; wherein the first filter has a ladder filter structure including one or more series resonators disposed on the first path and one or more parallel resonators disposed on a path connecting the first path and ground; a series resonator that is closest to the common terminal among the one or more series resonators includes:
an IDT electrode that excites elastic waves; and
a reflector that reflects the elastic waves excited by the IDT electrode; and
a distance between the IDT electrode and the reflector is greater than or equal to about 0.44λ and less than about 0.5λ where λ is a wavelength of the elastic waves that is defined by an electrode cycle of the IDT electrode.

2 . The multiplexer according to claim 1 , wherein in the series resonator that is closest to the common terminal among the one or more series resonators, the distance between the IDT electrode and the reflector is less than or equal to about 0.48λ.

3 . The multiplexer according to claim 1 , wherein the reflector is disposed in a direction in which the elastic waves propagate with respect to the IDT electrode.

4 . The multiplexer according to claim 1 , wherein the first filter has a ladder filter structure including a plurality of stages.

5 . The multiplexer according to claim 1 , wherein the first filter further includes a longitudinally-coupled filter structure disposed on the first path.

6 . The multiplexer according to claim 1 , further comprising:
a piezoelectric film including a main surface on which the IDT electrode and the reflector are provided; a high-acoustic-velocity supporting substrate in which an acoustic velocity of bulk waves propagating therethrough is higher than an acoustic velocity of elastic waves propagating through the piezoelectric film; and a low-acoustic-velocity film disposed between the high-acoustic-velocity supporting substrate and the piezoelectric film, in which an acoustic velocity of bulk waves propagating through the low-acoustic-velocity film is lower than the acoustic velocity of bulk waves propagating through the piezoelectric film.

7 . The multiplexer according to claim 1 , wherein the multiplexer is defined by a first duplexer including two filters including the first filter and a second duplexer including two filters including the second filter.

8 . The multiplexer according to claim 1 , wherein
the passband of the first filter is an uplink frequency band of Band 3; and the passband of the second filter is an uplink frequency band of Band 1.

9 . A radio-frequency front-end circuit comprising:
the multiplexer according to claim 1 ; and an amplifier circuit connected to the multiplexer.

10 . The radio-frequency front-end circuit according to claim 9 , wherein in the series resonator that is closest to the common terminal among the one or more series resonators, the distance between the IDT electrode and the reflector is less than or equal to about 0.48λ.

11 . The radio-frequency front-end circuit according to claim 9 , wherein the reflector is disposed in a direction in which the elastic waves propagate with respect to the IDT electrode.

12 . The radio-frequency front-end circuit according to claim 9 , wherein the first filter has a ladder filter structure including a plurality of stages.

13 . The radio-frequency front-end circuit according to claim 9 , wherein the first filter further includes a longitudinally-coupled filter structure disposed on the first path.

14 . The radio-frequency front-end circuit according to claim 9 , further comprising:
a piezoelectric film including a main surface on which the IDT electrode and the reflector are provided; a high-acoustic-velocity supporting substrate in which an acoustic velocity of bulk waves propagating therethrough is higher than an acoustic velocity of elastic waves propagating through the piezoelectric film; and a low-acoustic-velocity film disposed between the high-acoustic-velocity supporting substrate and the piezoelectric film, in which an acoustic velocity of bulk waves propagating through the low-acoustic-velocity film is lower than the acoustic velocity of bulk waves propagating through the piezoelectric film.

15 . The radio-frequency front-end circuit according to claim 9 , wherein the multiplexer is defined by a first duplexer including two filters including the first filter and a second duplexer including two filters including the second filter.

16 . The radio-frequency front-end circuit according to claim 9 , wherein
the passband of the first filter is an uplink frequency band of Band 3; and the passband of the second filter is an uplink frequency band of Band 1.

17 . A communication apparatus comprising:
an RF signal processing circuit that processes a radio frequency signal transmitted and received by an antenna element; and the radio-frequency front-end circuit according to claim 9 , the radio-frequency front-end circuit transferring the radio frequency signal between the antenna element and the RF signal processing circuit.

18 . The communication apparatus according to claim 17 , wherein in the series resonator that is closest to the common terminal among the one or more series resonators, the distance between the IDT electrode and the reflector is less than or equal to about 0.48λ.

19 . The communication apparatus according to claim 17 , wherein the reflector is disposed in a direction in which the elastic waves propagate with respect to the IDT electrode.

20 . The communication apparatus according to claim 17 , wherein the first filter has a ladder filter structure including a plurality of stages.

Assignees

• Murata Manufacturing Co

Inventors

• Takamine Yuichi

Classifications

• H03H9/725

  Duplexers · CPC title

• H03H9/6483 Primary

  Ladder SAW filters · CPC title

• H03H9/706

  Duplexers · CPC title

• H03H9/02574

  of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate · CPC title

• H04B1/52

  Hybrid arrangements, i.e. arrangements for transition from single-path two-direction transmission to single-direction transmission on each of two paths or vice versa · CPC title