1. Introduction to the algorithm
Automatic Gain Control;
An automatic control method that automatically adjusts the gain of the amplifier circuit with the signal strength.
The circuit that realizes this function is called AGC ring for short. The AGC loop is a closed-loop electronic circuit, which can be divided into two parts: a gain-controlled amplifying circuit and a control voltage forming circuit. The gain-controlled amplifier circuit is located in the forward amplifier path, and its gain varies with the control voltage.
The basic components of the control voltage forming circuit are AGC detectors and low-pass smoothing filters, and sometimes gate circuits and DC amplifiers are included. After the output signal u0 of the amplifying circuit is detected and filtered out by a filter to remove low-frequency modulation components and noise, a voltage uc for controlling the gain-controlled amplifier is generated. When the input signal ui increases, u0 and uc also increase.
The increase of uc reduces the gain of the amplifier circuit, so that the change of the output signal is significantly smaller than the change of the input signal, and the purpose of automatic gain control is achieved. The control methods for the gain of the amplifier circuit are as follows:
①Change the DC working state of the transistor to change the current amplification factor β of the transistor. ②Insert electronically controlled attenuators between all levels of the amplifier. ③ Use electronically controlled variable resistors as amplifier loads, etc. AGC circuit is widely used in various receivers, recorders and measuring instruments. It is often used to keep the output level of the system within a certain range, so it is also called automatic level control; when used in voice amplifiers or radios, it is called automatic level control. for automatic volume control.
2. Part of the core code
3. Simulation screenshots and simulation video demonstrations
4. Relevant references
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A01-21