Tunable Impedance Matching Circuit

• US 20100164645A1
• Filed: 09/14/2007
• Published: 07/01/2010
• Est. Priority Date: 09/14/2007
• Status: Abandoned Application

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Watanabe, Yuu, Kobayashi, Kazuhiko, Kayal, Maher, Dal Fabbro, Paulo Augusto
• Application Number:
  US12/676,335
• Publication Number:
  US 20100164645A1
• Time in Patent Office: Days
• US Class Current: 333/32
• CPC Class Codes: H03F 1/565 using inductive elements
• CPC Class Codes: H03F 2200/144 the feedback circuit of the amplifier stage comprising a passive resistor and passive capacitor
• CPC Class Codes: H03F 2200/222 A circuit being added at the input of an amplifier to adapt the input impedance of the amplifier
• CPC Class Codes: H03F 2200/387 A circuit being added at the output of an amplifier to adapt the output impedance of the amplifier
• CPC Class Codes: H03F 2200/391 the output circuit of an amplifying stage comprising an LC-network
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2200/453 Controlling being realised by adding a replica circuit or by using one among multiple identical circuits as a replica circuit
• CPC Class Codes: H03F 2200/456 A scaled replica of a transistor being present in an amplifier
• CPC Class Codes: H03F 2200/541 Transformer coupled at the output of an amplifier
• CPC Class Codes: H03F 3/195 in integrated circuits
• CPC Class Codes: H03H 11/40 Impedance converters
• CPC Class Codes: H03H 7/38 Impedance-matching networks

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 I_control 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 I_control. 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 I_control relative to output current I_RF of RF PA 11.

Claims

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.

2. 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.

3. 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.

4. 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.

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

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

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

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

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