Patent ID: 7676208

Claim:
An automatic gain control device for automatically controlling a gain of a plurality of first signals input through a plurality of antennas in a wireless communication system, the automatic gain control device comprising: a radio frequency receiver for receiving the first signals through the antennas, respectively controlling gains of the first signals, and outputting the first signals having the controlled gain as a plurality of second signals through a plurality of analog to digital converters (ADCs); a signal saturation detecting unit for outputting a saturation index determination value when the number of the first signals that are greater than a threshold value is found to be greater than a predetermined number; and a gain controlling unit for comparing power values of the first signals to detect a greatest power value from among the first signals and configured to output a gain value determined based on a detected greatest power value and the saturation index determination value to the radio frequency receiver, wherein when the saturation index determination value indicates that a number of saturated ADCs is greater than a saturation count reference value then the gain value is reduced, when the number of saturated ADCs is less than the saturation count reference value and when the detected greatest power value is higher than a target power value then the gain value is reduced, when the number of saturated ADCs is less than the saturation count reference value and when the detected greatest power value is lower than the target power value then the gain value is set to be equal to a register value, wherein the gain controller controlling unit comprises: a power measuring unit for comparing a plurality of absolute power values of the first signals, detecting the greatest absolute power value from among the compared absolute power values, and outputting the detected greatest absolute power value as a logarithmic power value; a low noise amplifier (LNA) state determining unit for calculating a low noise amplifier state control index based on a current-LNA state determination value and a current gain value, determining a subsequent LNA state determination value, and outputting the determined subsequent LNA state determination value as a gain control state determination value; and a gain determining unit for receiving the logarithmic power value output from the power measuring unit, the saturation index determination value input from the signal saturation detecting unit, the LNA state determination value, the LNA state determination value, a first gain control value, and a second gain control value, and outputting a finally controlled gain determination value.