Composite filter device

Patent metadata

Field	Value
Publication number	US-12028052-B2
Application number	US-202017080903-A
Country	US
Kind code	B2
Filing date	Oct 27, 2020
Priority date	Nov 18, 2019
Publication date	Jul 2, 2024
Grant date	Jul 2, 2024

Abstract

A composite filter device includes a transmission filter and a reception filter first and second acoustic wave filters, respectively. The first acoustic wave filter has a first pass band and the second acoustic wave filter has a second pass band higher than the first pass band. One end of the first acoustic wave filter and one end of the second acoustic wave filter are connected in common by a common terminal. The second acoustic wave filter is a ladder filter including parallel arm resonators defined by acoustic wave resonators. The inequalities of fq<fr and fr<fp<fa are satisfied, where fq and fp represent a resonant frequency and an anti-resonant frequency, respectively, of one of the parallel arm resonators having the lowest capacitance and fr and fa represent resonant frequencies and anti-resonant frequencies, respectively, of other ones of the parallel arm resonators.

First claim

What is claimed is:

1. A composite filter device comprising:
a first acoustic wave filter having a first pass band; and
a second acoustic wave filter having a second pass band higher than the first pass band; wherein
one end of the first acoustic wave filter and one end of the second acoustic wave filter are connected in common by a common terminal;
the second acoustic wave filter is a ladder filter including a plurality of parallel arm resonators defined by acoustic wave resonators;
fq<fr and fr<fp<fa are satisfied, where fq and fp represent a resonant frequency and an anti-resonant frequency, respectively, of a first one of the plurality of parallel arm resonators which has a lowest capacitance of the plurality of parallel arm resonators and fr and fa represent resonant frequencies and anti-resonant frequencies, respectively, of other ones of the plurality of parallel arm resonators other than the first one of the plurality of parallel arm resonators having the lowest capacitance; and
of the plurality of parallel arm resonators, the first one of the plurality of parallel arm resonators is farthest from the common terminal.

2. The composite filter device according to claim 1 , wherein the second acoustic wave filter is a reception filter.

3. The composite filter device according to claim 2 , wherein
the common terminal is to be connected to an antenna; and
the first one of the plurality of parallel arm resonators having the lowest capacitance is different from a second one of the plurality of parallel arm resonators that is nearest to the common terminal of the plurality of parallel arm resonators.

4. The composite filter device according to claim 3 , wherein
the first one of the plurality of parallel arm resonators and the second one of the plurality of parallel arm resonators are connected in parallel; and
a series arm resonator is connected between a ground and a node between the first and second ones of the plurality of parallel arm resonators.

5. The composite filter device according to claim 1 , wherein the second acoustic wave filter is a surface acoustic wave filter.

6. The composite filter device according to claim 1 , the first acoustic wave filter is a transmission filter.

7. The composite filter device according to claim 1 , wherein
the first pass band is about 705.5 MHz to about 745.5 MHz; and
the second pass band is about 760.5 MHz to about 800.5 MHz.

8. The composite filter device according to claim 1 , wherein the second acoustic wave filter further includes a plurality of series arm resonators defined by acoustic wave resonators.

9. The composite filter device according to claim 1 , wherein
the first acoustic wave filter is a Band28 transmission filter; and
the second acoustic wave filter is a Band28 reception filter.

10. The composite filter device according to claim 1 , wherein the plurality of parallel arm resonators includes at least three parallel arm resonators.

11. The composite filter device according to claim 1 , wherein another end of the first acoustic wave filter and another end of the second acoustic wave filter are not directly connected in common.

12. The composite filter device according to claim 1 , wherein the composite filter device is configured to function as a duplexer or a multiplexer.

Assignees

• Murata Manufacturing Co

Inventors

• Nakamura Shinichi

Classifications

• H03H9/6483

  Ladder SAW filters · CPC title

• H03H9/725 Primary

  Duplexers · CPC title