Radio transmitter having an output power control circuit

摘要

A radio transmitter has an output power control circuit including a power amplifier, a directional coupler coupled to the power amplifier, a detector of the forward power of the directional coupler, a generator of a difference voltage between the output voltage of the detector means and a reference voltage. A power regulator varys the output power of the power amplifier in response to the output of the difference voltage. The power applied from the power amplifier through the directional coupler to the detector is controlled by a control signal. The control circuit electrically varies the coupling coefficient of the directional coupler for attenuating the power applied from the directional coupler to the detector means to extend the controllable range of the transmitter output power.