Radio frequency power amplifier

1. A radio frequency power amplifier, comprising:

an amplifying element that amplifies a radio frequency signal having a first frequency;

an input matching circuit connected to an input terminal of the amplifying element;

an output matching circuit connected to an output terminal of the amplifying element; and

a reactance control circuit having one end connected to an output terminal of the amplifying element, and the other end connected to an input terminal of the output matching circuit and to a direct current power source terminal,

wherein the amplifying element is a field effect transistor including a gate electrode, a drain electrode, and a source electrode,

at least one of the gate electrode or the source electrode has a field-plate structure,

the reactance control circuit has a reactance which resonates at a second frequency with a parasitic capacitance of the amplifying element at the output terminal of the amplifying element,

the parasitic capacitance of the amplifying element is a parasitic capacitance held by the amplifying element calculated from inter-electrode parasitic capacitances between the gate electrode, the drain electrode and the source electrode,

a parasitic capacitance C of the amplifying element is expressed by an equation

C

=

Cds

+

Cgs

×

Cdg

Cgs

×

Cdg

where Cgs is a parasitic capacitance between the gate electrode and the source electrode, Cdg is a parasitic capacitance between the drain electrode and the gate electrode, and Cds is a parasitic capacitance between the drain electrode and the source electrode, and

the second frequency is identical or close to the first frequency.

2. The radio frequency power amplifier according to claim 1 ,

wherein the second frequency is a frequency at which a power added efficiency is higher in the radio frequency power amplifier than in another radio frequency power amplifier that does not include the reactance control circuit.

3. The radio frequency power amplifier according to claim 1 ,

wherein the first frequency is from 2.4 to 2.5 GHz, and

the second frequency is 0.82 to 2.4 times the first frequency.

4. The radio frequency power amplifier according to claim 3 ,

wherein the second frequency is 0.87 to 1.9 times the first frequency.

5. The radio frequency power amplifier according to claim 1 ,

wherein the first frequency is from 1 to 5 GHz, and

the second frequency is 0.92 to 1.8 times the first frequency.

6. The radio frequency power amplifier according to claim 5 ,

wherein the second frequency is 0.93 to 1.4 times the first frequency.

7. The radio frequency power amplifier according to claim 1 ,

wherein the second frequency is higher than the first frequency.

8. The radio frequency power amplifier according to claim 1 ,

wherein the reactance control circuit includes an inductor.

9. The radio frequency power amplifier according to claim 1 ,

wherein the reactance control circuit includes a transmission line.

10. The radio frequency power amplifier according to claim 9 ,

wherein the transmission line is a microstrip line or a coplanar line.

11. The radio frequency power amplifier according to claim 1 ,

wherein the reactance control circuit includes a serial resonator having a capacitor and an inductor.

12. The radio frequency power amplifier according to claim 1 ,

wherein the reactance control circuit includes an open stub.

13. The radio frequency power amplifier according to claim 1 ,

wherein the amplifying element is a field effect transistor made of a compound semiconductor.

14. The radio frequency power amplifier according to claim 1 ,

wherein the amplifying element is a field effect transistor having a GaN/AlGaN heterojunction.