Antenna matching circuit, antenna circuit, front-end circuit, and communication apparatus

Patent metadata

Field	Value
Publication number	US-10424841-B2
Application number	US-201815883593-A
Country	US
Kind code	B2
Filing date	Jan 30, 2018
Priority date	Jul 31, 2015
Publication date	Sep 24, 2019
Grant date	Sep 24, 2019

Abstract

The present disclosure includes a first circuit that is connected between a power feed port and an antenna port, and a second circuit that is connected between the power feed port and the ground or between the antenna port and the ground. The first circuit is a circuit in which for example a first variable capacitance element is connected in series with a first inductor, and the second circuit is a circuit in which for example a second variable capacitance element is connected in parallel with a second inductor. A switch performs switching at least between a first state in which a second end of the second circuit is connected to a first end of the first circuit and a second state in which the second end of the second circuit is connected to a second end of the first circuit.

First claim

The invention claimed is:

1. An antenna matching circuit including a first circuit that is connected between a power feed port and an antenna port, and a second circuit that is connected between the power feed port and ground or between the antenna port and ground, the antenna matching circuit comprising:
a switch configured to selectively connect the second circuit between a first state and a second state, the first state connecting the second circuit between a first end of the first circuit and ground, and the second state connecting the second circuit between a second end of the first circuit and ground,
wherein the first end of the first circuit is connected to the power feed port and the second end of the first circuit is connected to the antenna port, and
wherein according to an expression of an impedance of an antenna connected to the antenna port using a reflection coefficient:
the switch connects the second circuit in the first state when a real part of the reflection coefficient is negative, and
the switch connects the second circuit in the second state when the real part of the reflection coefficient is positive.

2. The antenna matching circuit according to claim 1 , wherein:
the first circuit comprises a first variable capacitance element connected in series with a first inductor, and
the second circuit comprises a second variable capacitance element connected in parallel with a second inductor.

3. The antenna matching circuit according to claim 2 , wherein the first variable capacitance element, the second variable capacitance element, and the switch are included in a single integrated circuit.

4. An antenna circuit comprising:
the antenna matching circuit according to claim 1 ; and
a first antenna that is connected to the antenna port and that is for a first communication frequency band.

5. The antenna circuit according to claim 4 , further comprising:
a second antenna for a second communication frequency band, the second communication frequency band being higher than the first communication frequency band;
a second power feed circuit that is connected to the second antenna and that is for the second communication frequency band; and
a low pass filter at the antenna port, wherein the low pass filter has a cutoff frequency between the first communication frequency band and the second communication frequency band.

6. The antenna circuit according to claim 5 , wherein the low pass filter has an impedance transformation function for the first antenna and the antenna matching circuit.

7. The antenna circuit according to claim 5 , further comprising a high pass filter between the second power feed circuit and the second antenna, wherein the high pass filter has a cutoff frequency between the first communication frequency band and the second communication frequency band is provided.

8. The antenna circuit according to claim 7 , wherein the high pass filter has an impedance transformation function for the second antenna and the second power feed circuit.

9. A communication apparatus comprising:
an antenna circuit according to claim 4 ; and
a communication circuit connected to the antenna circuit.

10. A front-end circuit comprising:
the antenna matching circuit according to claim 1 ; and
a high-frequency circuit connected to the antenna matching circuit.

11. The front-end circuit according to claim 10 , wherein the high-frequency circuit comprises a power amplifier configured to amplify a transmission signal.

12. An antenna circuit comprising:
a diplexer having a low pass filter between a first port and a third port, and a high pass filter between a second port and the third port;
an antenna connected to the third port of the diplexer;
a first power feed circuit configured to feed power to the antenna via the first port of the diplexer;
a second power feed circuit configured to feed power to the antenna via the second port of the diplexer; and
an antenna matching circuit according to claim 1 between the first power feed circuit and the first port of the diplexer.

13. The antenna circuit according to claim 12 , wherein the low pass filter has an impedance transformation function for the antenna and the antenna matching circuit, or the high pass filter has an impedance transformation function for the antenna and the antenna matching circuit.

Assignees

• Murata Manufacturing Co

Inventors

• Kuroda Katsuhito
• Onaka Kengo

Classifications

• H03H7/175

  Series LC in series path (H03H7/1783 takes precedence) · CPC title

• H04B1/0458

  Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages (matching circuits in general H03H) · CPC title

• H01Q5/50

  Feeding or matching arrangements for broad-band or multi-band operation · CPC title

• H03H7/1775

  Parallel LC in shunt or branch path (H03H7/1791 takes precedence) · CPC title

• H01Q9/42

  with folded element, the folded parts being spaced apart a small fraction of the operating wavelength · CPC title