Patent ID: 8369466

Claim:
An automatic gain control circuit comprising: an amplification degree control section for calculating power of a digital value of a received signal, and for controlling an amplification degree of an amplifier of a receiving apparatus so that a difference between the power and predetermined reference power is zero; a received signal quality measuring section for measuring quality of the received signal; a reference power adjusting section for, upon finding that the measured quality of the received signal is below a fixed level, adjusting the reference power for a predetermined period of time; and a reference power updating section for causing the reference power adjusting section to continue to adjust the reference power until the quality of the received signal recovers to be at a predetermined recovery level or above, and for updating the reference power so that the reference power takes on an optimally adjusted value, wherein the reference power adjusting section reads, as the fixed level and the predetermined recovery level, an individual threshold stored beforehand in accordance with modulation method information or coding rate information extracted from a control signal contained in the received signal, and uses the threshold for determining the quality of the received signal.