Just like a Phase-Locked Loop (PLL) automatically tracks the carrier phase of this wireless signal in a feedback loop, an Automatic Gain Control (AGC) performs a similar task for the amplitude. After the moving average filter, a reference level $R$ is divided by the input signal magnitude so that when it is multiplied with the input signal in the next step, the output signal is automatically set to amplitude $R$. On other hand, a log AGC tracks the input signal within a prescribed time, regardless of the signal level.