Patent ID: 8633761

Claim:
A power amplifier comprising: a power amplification circuit which amplifies an input signal; an output matching circuit connected to an output terminal of the power amplification circuit configured to perform impedance matching between the power amplification circuit and an antenna load; and a 4-port coupler connected between the output matching circuit and the antenna load, the 4-port coupler comprising: an input port having a reflection coefficient ┌ PA based on an incident signal a 1 and a reflection signal b 1 , an output port having a reflection coefficient ┌ L based on an incident signal a 2 and a reflection signal b 2 , a coupled port having a reflection coefficient ┌ D based on an incident signal a 3 and a reflection signal b 3 , and an isolation port having a reflection coefficient ┌ CT based on an incident signal a 4 and a reflection signal b 4 , wherein the reflection coefficient ┌ D and the reflection coefficient ┌ CT are determined so that the reflection coefficient ┌ PA is not changed when ┌ L is changed.