# US 2010/0164645 A1 · Tunable Impedance Matching Circuit

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- Number: US 2010/0164645 A1
- Document ID: US20100164645A1
- Status: Published application
- Kind: A1
- Application number: 12/676,335
- Filed: 2007-09-14
- Published: 2010-07-01
- Earliest claimed: 2007-09-14
- Assignees: Fujitsu Limited
- Inventors: Kazuhiko Kobayashi; Yuu Watanabe; Paulo Augusto Dal Fabbro; Maher Kayal
- Web page: https://patentgrep.com/patent/US20100164645A1

## CPC

- H03F 1/565: {using inductive elements}
- H03F 3/195: in integrated circuits
- H03H 7/38: Impedance-matching networks
- H03H 11/40: Impedance converters
- H03F 2200/144: the feedback circuit of the amplifier stage comprising a passive resistor and passive capacitor
- H03F 2200/222: A circuit being added at the input of an amplifier to adapt the input impedance of the amplifier
- H03F 2200/387: A circuit being added at the output of an amplifier to adapt the output impedance of the amplifier
- H03F 2200/391: the output circuit of an amplifying stage comprising an LC-network
- H03F 2200/451: the amplifier being a radio frequency amplifier
- H03F 2200/453: Controlling being realised by adding a replica circuit or by using one among multiple identical circuits as a replica circuit
- H03F 2200/456: A scaled replica of a transistor being present in an amplifier
- H03F 2200/541: Transformer coupled at the output of an amplifier
- H03F: AMPLIFIERS
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)

## Abstract

The tunable impedance circuit comprises capacitors C1 and C2, an inductor L1, and an inductor L2 magnetically coupled with the inductor L1. The control current Icontrol with variable phase and amplitude from the control circuit 13 flows in the inductor L2. The impedance of the inductor L1 is changed by changing the phase and amplitude of the control current Icontrol. The output impedance is set to an optimum level by setting an effective inductance and an effective quality factor of the tunable impedance circuit 12a to be optimum by means of the phase and amplitude of the control current Icontrol relative to output current IRF of RF PA 11.

## Claims

### Claim 1

A tunable impedance matching circuit adjusting an impedance of an input or output of an external circuit, comprising:
a first inductor for conducting a current of the external circuit;
a capacitor unit connected to the first inductor;
a second inductor magnetically coupled with the first inductor, for conducting a control current with a certain phase and amplitude relative to the current of the external circuit; and
a control circuit for applying the control current to the second inductor and changing the impedance of the first inductor magnetically coupled with the second inductor by changing either or both of the phase and amplitude of the control current.

### Claim 2 (depends on 1)

The tunable impedance matching circuit according to claim 1, wherein
the capacitor unit includes
a first capacitor connected at an input of the first inductor; and
a second capacitor connected at an output of the first inductor.

### Claim 3 (depends on 1)

The tunable impedance matching circuit according to claim 1, wherein
the control circuit sets the phase and the amplitude of the control current so that a quality factor of a circuit comprising the first inductor and the capacitor unit becomes optimum.

### Claim 4 (depends on 1)

The tunable impedance matching circuit according to claim 1, wherein
a frequency of the control current is equal to that of the current of the external circuit.

### Claim 5 (depends on 1)

The tunable impedance matching circuit according to claim 1 connected at an output of the external circuit.

### Claim 6 (depends on 1)

The tunable impedance matching circuit according to claim 1 connected at an input of the external circuit.

### Claim 7 (depends on 1)

A frequency tunable amplifier configured with the tunable impedance matching circuit according to claim 1.

### Claim 8 (depends on 1)

A frequency tunable amplifier connected with the tunable impedance matching circuit according to claim 1 at its input.

### Claim 9 (depends on 1)

A frequency tunable amplifier connected with the tunable impedance matching circuit according to claim 1 at its output.