Automatic gain control system and method applicable to WiFi receiver

The invention discloses an automatic gain control system and method applicable to a WiFi receiver. The gain is adjusted by using a digital closed loop structure, a baseband ADC collectors a WiFi baseband signal, a power estimation link estimates the power on the WiFi signal, a gain adjustment link adjusts the gain of a variable gain module according to the amplitude of the power output in the power estimation link so as to generate a gain control signal, and the gain control signal directly acts on the variable gain control module, so that the effective amplitude of the adjusted signal is stabilized near the target value. According to the automatic gain control system and method, in view of the condition of high peak-to-average ratio and a short training sequence of 8us time length, a power level estimation and gain adjustment method is provided, the common automatic gain control technology is analyzed, an improved digital filter is used for estimating the power so as to avoid the errors caused by I, Q mismat