Patent ID: 8909183

Claim:
An automatic gain control device comprising: a first frequency converter that generates an I-system baseband signal based on a high-frequency received signal and a first local signal with a predetermined frequency band; a second frequency converter that generates a Q-system baseband signal based on the high-frequency received signal and a second local signal 90° out of phase with the first local signal; a first variable amplifier that amplifies the generated I-system baseband signal; a second variable amplifier that amplifies the generated Q-system baseband signal; a first AD converter that coverts the amplified I-system baseband signal into a digital signal; a second AD converter that coverts the amplified Q-system baseband signal into a digital signal; a first over-range detector that detects an over-range of the first AD converter; a second over-range detector that detects an over-range of the second AD converter; an automatic gain controller that selects gains set in the first variable amplifier and the second variable amplifier based on detection information about the over-range, the I-system baseband signal or the Q-system baseband signal; and an offset setter that sets gains which are obtained by giving a predetermined offset to the selected gains in the first variable amplifier or the second variable amplifier in a gain control, and sets the selected gains in the first variable amplifier or the second variable amplifier in a subsequent gain control following after the gain control.