Patent ID: 6728524
Filing Date: 2004-04-27
Classification: H03G

Abstract:
An automatic gain control circuit installed in a demodulation system that includes a first variable gain amplifier, a second variable gain amplifier, an A/D converter for carrying out analog-to-digital conversion of a modulation wave and a demodulator for demodulating the modulation wave to recover transmitted digital data, said automatic gain control circuit controlling a gain of the first variable gain amplifier and a gain of the second variable gain amplifier to maintain average amplitude of the modulation wave to be supplied to the A/D converter at a fixed value, said automatic gain control circuit comprising:a power calculator for calculating power of a modulation wave supplied to the demodulator; a power comparator for comparing the power calculated by said power calculator with ideal power of a modulation scheme of the modulation signal; a first gain controller for carrying out gain control of the first variable gain amplifier in response to an output of said power comparator; and a second gain controller for carrying out gain control of the second variable gain amplifier in response to the output of said power comparator and independently of the first gain controller.