Patent ID: 7110735

Claim:
An automatic gain control system comprising: a radio-frequency amplifier; a local oscillator; a mixing unit that combines an output signal from said radio-frequency amplifier and an output signal from said local oscillator and generates an intermediate-frequency signal; a bandpass filter that limits a bandwidth of said intermediate-frequency signal; an intermediate-frequency amplifier that amplifies an output signal from said bandpass filter; a power detector that detects a power of the output signal from said radio-frequency amplifier; a filtering unit that filters an output signal from said power detector; an adder that adds an output signal from said filtering unit and an output signal from said intermediate-frequency amplifier; an A/D converter that converts an output signal from said adder from analog to digital; and a controller that adjusts a gain of said radio-frequency amplifier and a gain of said intermediate-frequency amplifier based on an output signal from said A/D converter.