Patent ID: 6498925
Filing Date: 2002-12-24
Classification: H03F,H04W

Abstract:
A transmit power control circuit comprising:a variable gain circuit for inputting a radio-frequency signal, for amplifying the radio-frequency signal with a gain which changing based on an external control signal, and for outputting an amplified radio-frequency signal as an output signal; a first switching circuit for selecting one of a main transmission line and an auxiliary transmission line, and for outputting the output signal of the variable gain circuit to the one of the main transmission line and the auxiliary transmission line; an amplifying circuit provided to the main transmission line, and for amplifying the output signal of the variable gain circuit, which being outputted to the main transmission line; a directional coupler coupled with the main transmission line with a predetermined amount of coupling, and having one end and another end; a second switching circuit for connecting the one end of the directional coupler to a first terminator when the output signal of the variable gain circuit is outputted to the main transmission line, and for connecting the one end of the directional coupler to the auxiliary transmission line when the output signal of the variable gain circuit is outputted to the auxiliary transmission line; and a third switching circuit for connecting said another end of the directional coupler to a wave detector when the output signal of the variable gain circuit is outputted to the main transmission line, and for connecting said another end of the directional coupler to a second terminator when the output signal of the variable gain circuit is outputted to the auxiliary transmission line.