HIGH-FREQUENCY FILTER, FRONT-END CIRCUIT, AND COMMUNICATION APPARATUS

• US 20180019731A1
• Filed: 09/28/2017
• Published: 01/18/2018
• Est. Priority Date: 03/30/2015
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Tsukamoto, Hideki, Tani, Masakazu
• Granted Patent: US 10,200,012 B2
• Time in Patent Office: Days
• CPC Class Codes: H03H 9/0009 using surface acoustic wave devices
• CPC Class Codes: H03H 9/542 including passive elements H03H9/545 takes precedence
• CPC Class Codes: H03H 9/6403 Programmable filters
• CPC Class Codes: H03H 9/6406 Filters characterised by a particular frequency characteristic
• CPC Class Codes: H03H 9/6423 Means for obtaining a particular transfer characteristic
• CPC Class Codes: H03H 9/6483 Ladder SAW filters
• CPC Class Codes: H03H 9/706 Duplexers
• CPC Class Codes: H03H 9/725 Duplexers

Abstract

A high-frequency filter (10) includes resonators (21, 31, and 32), an inductor (41), and a switch (51). The resonator (21) is connected between a first input/output terminal (P1) and a second input/output terminal (P2). One end of the inductor (41) is connected between the resonator (21) and the first input/output terminal (P1). One end of the resonator (31) is connected to the other end of the inductor (41). The switch (51) selects either a connection portion that connects the inductor (41) and the resonator (31) or the resonator (32) and connects either the connection portion or the resonator (32), which has been selected, to a terminal of the resonator (21) on the side of the second input/output terminal (P2). The switching between the connection modes of the switch (51) changes the circuit configuration of the high-frequency filter (10).

Claims

1. A high-frequency filter comprising:

a first resonator connected between a first input/output terminal and a second input/output terminal;

a first reactance element having one end connected between the first resonator and the first input/output terminal;

a second resonator having one end connected to another end of the first reactance element;

a third resonator; and

a switch configured to select either the third resonator or a connection portion connecting the first reactance element to the second resonator and connecting a selected one of the third resonator and the connection portion to a terminal of the first resonator on a side of the second input/output terminal.

2. The high-frequency filter according to claim 1, wherein the second resonator and the third resonator are connected to a ground.

3. The high-frequency filter according to claim 1, wherein the switch connects an unselected one of the third resonator and the connection portion to the ground.

4. The high-frequency filter according to claim 1, further comprising a second reactance element connected in parallel to the third resonator.

5. The high-frequency filter according to claim 1, further comprising:

a fourth resonator connected between a connection portion connecting the first resonator to the switch and the second input/output terminal; and

a third reactance element connected between a connection portion connecting the first reactance element to the second resonator and the second input/output terminal.

6. The high-frequency filter according to claim 1, wherein the first reactance element is an inductor.

7. The high-frequency filter according to claim 1, wherein the first reactance element is a capacitor.

8. The high-frequency filter according to claim 5, wherein the first reactance element, the second reactance element, and the third reactance element are inductors.

9. The high-frequency filter according to claim 5, wherein the first reactance element and the third reactance element are capacitors.

12. A front-end circuit comprising:

a branching circuit including a transmission filter for performing filter processing upon a transmission signal and a reception filter for performing filter processing upon a reception signal;

a transmission-side amplification circuit connected to the transmission filter; and

a reception-side amplification circuit connected to the reception filter,

wherein at least one of the transmission filter and the reception filter is the high-frequency filter according to claim 1.

13. A communication apparatus comprising:

the front-end circuit according to claim 12; and

an RFIC connected to the transmission-side amplification circuit and the reception-side amplification circuit and generating a control signal for the switch.

14. The high-frequency filter according to claim 2, wherein the switch connects an unselected one of the third resonator and the connection portion to the ground.

15. The high-frequency filter according to claim 2, further comprising a second reactance element connected in parallel to the third resonator.

16. The high-frequency filter according to claim 3, further comprising a second reactance element connected in parallel to the third resonator.

17. The high-frequency filter according to claim 2, further comprising:

a fourth resonator connected between a connection portion connecting the first resonator to the switch and the second input/output terminal; and

a third reactance element connected between a connection portion connecting the first reactance element to the second resonator and the second input/output terminal.

18. The high-frequency filter according to claim 3, further comprising:

a fourth resonator connected between a connection portion connecting the first resonator to the switch and the second input/output terminal; and

a third reactance element connected between a connection portion connecting the first reactance element to the second resonator and the second input/output terminal.

19. The high-frequency filter according to claim 4, further comprising:

a fourth resonator connected between a connection portion connecting the first resonator to the switch and the second input/output terminal; and

a third reactance element connected between a connection portion connecting the first reactance element to the second resonator and the second input/output terminal.

20. The high-frequency filter according to claim 2, wherein the first reactance element is an inductor.

10. A high-frequency filter supporting a first communication band and a second communication band having a center frequency higher than the first communication band and partly overlapped with the first communication band, and including a first terminal and a second terminal, comprising:

a ladder resonant circuit placed between the first terminal and the second terminal and including one or more series arm resonators and one or more parallel arm resonators; and

a first attenuation circuit connected to a node between the ladder resonant circuit and the second terminal,

wherein the first attenuation circuit includes a resonator and a switch,

wherein one end of the resonator is connected to a first selection target terminal of the switch and another end of the resonator is connected to a ground potential,

wherein the switch includes the first selection target terminal connected to the resonator, a second selection target terminal connected to a ground, and a common terminal selectively connected to the first selection target terminal or the second selection target terminal and connected to the node, and

wherein the high-frequency filter switches between a state for a second communication band where the common terminal and the first selection target terminal of the switch are connected and a state for a first communication band where the common terminal and the second selection target terminal of the switch are connected.

11. The high-frequency filter according to claim 10, further comprising a longitudinally coupled resonant circuit including a plurality of longitudinally coupled resonators and connected in series to the ladder resonant circuit.