Power amplifier

A power amplifier amplifying a high frequency modulation signal including an amplitude modulation component and a phase-modulated component, comprising:

• an AD converter pulse modulating an envelope signal that the amplitude modulation component;
• a multiplier synthesizing a phase-modulated signal having a constant envelope that is the phase-modulated component and an output signal from the AD converter;
• a high frequency amplifier amplifying an output signal from the multiplier;
• a bandpass filter removing out-of-band noise from an output signal from the high frequency amplifier;
• and
• a voltage control device supplying a power supply voltage to the high frequency amplifier and changing the power supply voltage in accordance with a control signal for controlling an average power of an output signal from the high frequency amplifier, the control signal being supplied from the outside.

A power amplifying method for amplifying a high frequency modulation signal including an amplitude modulation component and a phase-modulated component, comprising:

• pulse modulating an envelope signal that is the amplitude modulation component in an AD (Analog to Digital) converter while controlling an average power of an input signal to the AD converter to be constant;
• amplifying an output signal from the AD converter in a switching amplifier having a power supply voltage that is changed in accordance with a control signal from the outside;
• enabling an output signal from the switching amplifier to pass through a low-pass filter, thereby removing high frequency noise;
• and
• synthesizing an output signal from the low-pass filter and an input signal in a high frequency amplifier having the output signal from the low-pass filter as a power supply, thereby obtaining a high frequency modulation signal after the amplification, the input signal being a high frequency modulation signal including at least the amplitude modulation component.

A power amplifying method for amplifying a high frequency modulation signal including an amplitude modulation component and a phase-modulated component, comprising:

• pulse modulating an envelope signal that is the amplitude modulation component in an AD converter;
• synthesizing a phase-modulated signal having a constant envelope that is the amplitude modulation component and an output signal from the AD converter with a multiplier;
• amplifying an output signal from the multiplier in a high frequency amplifier having a power supply voltage that is changed in accordance with a control signal for controlling an average power of an output signal from the high frequency amplifier, the control signal being supplied from the outside;
• and
• removing out-of-band noise from the output signal from the high frequency amplifier in a bandpass filter.