Abstract: A radio frequency signal having a constant amplitude is modulated by a digital modulation signal and a radio frequency input signal whose amplitude changes stepwise is generated. The radio frequency input signal is input into a power amplifier that is an evaluation target. A period in which an amplitude of the radio frequency input signal is constant is defined as a measurement period and an output signal of the power amplifier is measured in each of measurement periods in which amplitudes of the radio frequency input signal are different from each other.

Abstract: A power supply circuit supplies a variable voltage to a power amplifier that amplifies a radio-frequency signal, and includes a transistor and a current detecting resistor. The transistor includes a collector or drain that is supplied with a fixed voltage from a fixed voltage source, a base or gate that receives an envelope signal tracking an envelope of the radio-frequency signal, and an emitter or source that outputs the variable voltage that is based on the envelope signal. The current detecting resistor is electrically connected between the fixed voltage source and the collector or drain of the transistor.

Abstract: A power supply circuit supplies a variable voltage to a power amplifier that amplifies a radio-frequency signal, and includes a transistor and a current detecting resistor. The transistor includes a collector or drain that is supplied with a fixed voltage from a fixed voltage source, a base or gate that receives an envelope signal tracking an envelope of the radio-frequency signal, and an emitter or source that outputs the variable voltage that is based on the envelope signal. The current detecting resistor is electrically connected between the fixed voltage source and the collector or drain of the transistor.