Large signal performance of feedback automatic gain control systems

Feedback automatic gain control (FBAGC) is used to maintain the mean level of one or more signals throughout a signal processing system at a fixed value. The paper is particularly concerned with the application of FBAGC to receiver design and discusses the problem of attempting to suppress large unwanted envelope variations of an incoming signal without distorting any wanted modulation. A simple feedforward model of FBAGC systems predicts their effect on deep sinusoidal variations of the input signal´s envelope. Experimental results confirming the predictions are presented, and a method of determining the parameters of an undefined AGC system given. Finally, the fundamental problems of FBAGC dynamics are discussed, and a technique is suggested for greatly improving them.