ALC circuit for a transmitter device

摘要

An object of the present invention is to provide an ALC circuit for a transmitter device and a corresponding method which are capable of obtaining a detected voltage of sufficient and stable voltage over a wide high-frequency output power range. A signal extracted from a part of a transmission output signal by a directive coupler and a signal obtained by branching and amplifying a part of a local oscillation signal which is inputted to a first mixer for an up-convertor are inputted as a local oscillation signal of a second mixer. After the local oscillation signal has been down-converted into an intermediate frequency signal, it is inputted to a logarithmic amplifier through a band pass filter. The output signal of the logarithmic amplifier is extracted as a detected signal through a diode detector and amplified by a differential amplifier. The variable attenuator is controlled according to the amplified output to obtain a transmission output power. <IMAGE>