Patent ID: 7302022

Claim:
An AGC (automatic gain control) device in an OFDM (orthogonal frequency division multiplexing) system, comprising: an RF (radio frequency) unit for controlling a gain of an input signal; a first energy calculator for calculating an energy of output of the RF unit; a first accumulator for accumulating the energy calculated by the first energy calculator, finding a mean value thereof, and outputting the mean value; a second accumulator for accumulating output of the RF unit, calculating a mean value of the accumulated output and outputting the mean value as a DC offset; a second energy calculator for calculating an energy of the DC offset outputted by the second accumulator; a first subtractor for subtracting the energy of the DC offset of the input signal output by the second energy calculator from the energy of the input signal output by the first accumulator; and a second subtractor for subtracting a specific reference value established for AGC from an output of the first subtractor, and performing feedback of an output of the second subtractor for AGC to the RF unit.