Automatic gain control method and apparatus, and radio communications apparatus having automatic gain control function

摘要

At the power-on, a determination section (9) outputs a switch control signal (m) to a selector switch (7) to select the output of a sweep signal generator (6) which generates a voltage sweep signal (h) that increases from the minimum value to the maximum value of the gain control voltage range (p) at the same time, then provides the voltage sweep signal (h) to the variable gain amplifier (1), and calculates the difference (f) between the level detection value of an output signal (c) and a convergence value (e) and detects a sweep voltage value (j) obtained when (f) = 0 and stores the sweep voltage value (j) into memory. After the sweep operation, the sweep voltage value (j) stored in memory is provided as a gain control signal (b) to the variable gain amplifier (1). Then the primary automatic gain control via the closed loop control system is started.