An automatic frequency control (AFC) device is provided. The AFC device includes an input module, a received signal strength indicator (RSSI) module and a carrier frequency offset (CFO) estimation module. The input module down converts and samples a received signal. The RSSI module is coupled to the input module and calculates a RSSI signal in response to the down converted and sampled received signal. The CFO estimation module is coupled to the input module and the RSSI module and calculates a moving average of binary elements of the down converted and sampled received signal. The CFO estimation module continues to calculate the moving average until the AFC converges.