Patent ID: 8279983
Filing Date: 2012-10-02
Classification: H03G

Abstract:
1. An automatic gain control apparatus for providing a received signal with gain to control the signal level, comprising: a mean square processing means for performing mean square processing on the received signal over prescribed sampling intervals; a memory means for storing mean square values obtained by the mean square processing means; a gain coefficient generating means for generating a gain coefficient by dividing a preset reference output level by a mean value of a predetermined number of the mean square values stored in the memory means, at predetermined generating intervals; a decision means for deciding whether a received level of the received signal has changed; a gain coefficient generation control means for, when a change in the received level of the received signal is detected by the decision means, determining the number of the mean square values to be used in the generating of the gain coefficient by the gain coefficient generating means, and the generating interval; a gain coefficient alteration control means for altering the gain coefficient over an interval between the gain coefficient received from the gain coefficient generating means before an alteration and the gain coefficient received from the gain coefficient generating means after the alteration linearly and/or nonlinearly with a predetermined characteristic; and a multiplying means for multiplying the received signal by the gain coefficient received from the gain coefficient alteration control means; wherein if expressed by a graph in a coordinate system in which time is indicated on a horizontal axis and the gain coefficient is indicated on a vertical axis, the nonlinear characteristic of the gain coefficient alteration control means is a combination of an upwardly convex nonlinear function and a downwardly convex nonlinear function, when the gain coefficient received from the gain coefficient generating means after the alteration increases from the gain coefficient received from the gain coefficient generating means before the alteration, the gain coefficient alteration control means changes the downwardly convex nonlinear function to the upwardly convex nonlinear function during the interval between the gain coefficient received from the gain coefficient generating means before an alteration and the gain coefficient received from the gain coefficient generating means after the alteration, and when the gain coefficient received from the gain coefficient generating means after the alteration decreases from the gain coefficient received from the gain coefficient generating means before the alteration, the gain coefficient alteration control means changes the upwardly convex nonlinear function to the downwardly convex nonlinear function during the interval between the gain coefficient received from the gain coefficient generating means before an alteration and the gain coefficient received from the gain coefficient generating means after the alteration.