BRANCHING DEVICE

• US 20170194939A1
• Filed: 03/20/2017
• Published: 07/06/2017
• Est. Priority Date: 10/10/2014
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: MUKAI, Takao
• Granted Patent: US 10,128,815 B2
• Time in Patent Office: Days
• CPC Class Codes: H03H 9/0576 including surface acoustic wave [SAW] devices
• CPC Class Codes: H03H 9/64 using surface acoustic waves
• CPC Class Codes: H03H 9/70 Multiple-port networks for connecting several sources or loads, working on different frequencies or frequency bands, to a common load or source
• CPC Class Codes: H03H 9/725 Duplexers

Abstract

A branching device that separates signals of different pass bands increases attenuation characteristics outside the pass bands, and increases isolation characteristics. The branching device includes a duplexer including a transmission filter and a reception filter electrically connected to an antenna terminal, and a filter electrically connected to the antenna terminal. An inductor is electrically connected between the antenna terminal and a ground potential. The transmission filter is a ladder filter including serial arm resonators and parallel arm resonators, and each includes a polarized inductor electrically connected between the parallel arm resonators and a ground potential. The inductor and the polarized inductors inductively couple with each other, and a distance between the inductor and the polarized inductors is shorter than a distance between the polarized inductors.

Claims

1. A branching device comprising:

first, second, third, and fourth signal terminals;

a first filter, electrically connected to the first, second, and third signal terminals, the first filter providing first and second pass bands that are mutually different from each other;

a second filter, electrically connected to the first and fourth signal terminals, the second filter providing a third pass band that is different from the first and second pass bands;

a first inductor electrically connected between the first signal terminal and a ground potential;

a second inductor electrically connected between the first filter and a ground potential; and

a third inductor electrically connected between the second filter and a ground potential;

wherein

the first inductor inductively couples with the second inductor and the third inductor; and

each of a distance between the first inductor and the second inductor and a distance between the first inductor and the third inductor is shorter than a distance between the second inductor and the third inductor.

2. The branching device according to claim 1, wherein the distance between the first inductor and the second inductor is the same or substantially the same as the distance between the first inductor and the third inductor.

3. The branching device according to claim 1, wherein a coupling coefficient between the first inductor and the second inductor and a coupling coefficient between the first inductor and the third inductor are both within a range of greater than or equal to about 0.04 and less than or equal to about 0.07.

4. The branching device according to claim 1, wherein the first filter includes:

a first ladder filter that provides the first pass band and includes a first serial arm resonator and a first parallel arm resonator; and

a longitudinally coupled resonator filter that provides the second pass band.

5. The branching device according to claim 1, wherein the second filter includes a second ladder filter that provides the third pass band and includes a second serial arm resonator and a second parallel arm resonator.

6. The branching device according to claim 1, wherein:

the first filter includes a first serial arm resonator and a first parallel arm resonator;

the second filter includes a second serial arm resonator and a second parallel arm resonator;

the second inductor is electrically connected between the first parallel arm resonator and a ground potential; and

the third inductor is electrically connected between the second parallel arm resonator and a ground potential.

7. The branching device according to claim 1, wherein:

the first filter includes a plurality of first parallel arm resonators;

the second filter includes a plurality of second parallel arm resonators;

the second inductor is electrically connected between at least two parallel arm resonators of the plurality of first parallel arm resonators and a ground potential; and

the third inductor is electrically connected between at least two parallel arm resonators of the plurality of second parallel arm resonators and a ground potential.

8. The branching device according to claim 1, further comprising:

a fifth signal terminal;

wherein

the first filter includes;

a first filter portion that is electrically connected to the first and second signal terminals and provides the first pass band; and

a second filter portion that is electrically connected to the first and third signal terminals and provides the second pass band; and

the second filter includes;

a third filter portion that is electrically connected to the first and fourth signal terminals and provides the third pass band; and

a fourth filter portion that is electrically connected to the first and fifth signal terminals and provides a fourth pass band that is different from the third pass band.

9. The branching device according to claim 1, wherein:

the first, second, third and fourth signal terminals are provided on a circuit board;

the first filter is included in a first filter chip mounted on the circuit board;

the second filter is included in a second filter chip mounted on the circuit board;

the first inductor is included in an inductor chip mounted on the circuit board;

the second inductor is disposed on the circuit board to at least partially overlap with the first filter chip when the circuit board is viewed in plan view; and

the third inductor is disposed on the circuit board to at least partially overlap with the second filter chip when the circuit board is viewed in plan view.

10. The branching device according to claim 9, wherein the first filter chip and the inductor chip are electrically connected to each other by a first interconnect pattern on the circuit board.

11. The branching device according to claim 9, wherein the second filter chip and the inductor chip are electrically connected to each other by a second interconnect pattern on the circuit board.

12. The branching device according to claim 9, wherein the inductor chip is electrically connected to an antenna terminal by a third interconnect pattern on the circuit board.

13. The branching device according to claim 9, wherein the third inductor chip completely overlaps the second filter chip when the circuit board is seen in plan view.

14. The branching device according to claim 4, wherein the longitudinally coupled resonator filter is electrically connected to one end of a surface acoustic wave resonator.

15. The branching device according to claim 14, wherein another end of the surface acoustic wave resonator is electrically connected to an antenna terminal.

16. The branching device according to claim 8, wherein the second filter includes a longitudinally coupled resonator filter that provides the fourth pass band.

17. The branching device according to claim 6, wherein the second inductor and the third inductor provide a series electrical connection of a load capacitance.

18. The branching device according to claim 1, wherein at least one of the first and second pass bands is between about 704 MHz and about 716 MHz, between about 734 MHz and about 756 MHz, or between about 777 MHz and about 787 MHz.