All-Digital Automatic Gain Control Loop Based on Gain Decision

A long settling time of the all-digital automatic gain control (AGC) algorithm is obtained in a navigation receiver. To solve this problem, an improved AGC algorithm based on the gain decision is proposed in this paper. First, a mathematical model and loop settling time of the conventional AGC algorithm in the navigation receiver are analyzed. The contradiction between the loop settling time and the gain accuracy in the algorithm is shown. Accordingly, the proposed AGC algorithm based on the gain decision is examined. The algorithm calculates the deviation between the amplitudes of the output signal and reference value. Hence, the AGC loop can immediately adjust the gain when the amplitudes of the input signal change. In a comparison with the conventional AGC algorithm, the theoretical analysis and numerical simulation results verified that the proposed AGC algorithm can decrease the settling time without decreasing the gain accuracy of the AGC loop. The presented algorithm was implemented by a field-programmable gate array with low resource consumption and low complexity.