A fast convergence two-stage AGC for a Bluetooth low energy radio with 84dB tuning range

In recent years, Bluetooth low energy (BLE) has become a very popular standard for short range wireless communications. The simplified link control layer and concise packet structure make it very appealing to low power applications with medium data rate requirement. However, the very short preamble of a BLE packet is also present as a new design challenge. In such a burst data communication scenario, a short preamble means that only a very short time interval is allowed to adjust the gain of the receiver analog front end to condition the input signal strength to a proper level for decent demodulation in the digital baseband. Aiming at this problem, a fast convergence two-stage automatic gain control (AGC) loop is proposed in this paper. The algorithm is explained in details, and the performance is verified via simulation.