二次变频超外差接收机中自动增益控制电路的研究与设计

Research and Design of Automatic Gain Control Circuit in Double Conversion Superheterodyne Receiver

本文介绍了一种自动增益控制(AGC)电路,用于二次下变频超外差式接收前端的中频部分。该电路采用PIN二极管π形网络作为电调衰减器,肖特基二极管作为检波器,集成运算放大器用于产生控制电压。一中频电路与二中频电路均分布有电调衰减器。实验结果表明,对于20MHz带宽的中频信号,该自动增益控制电路控制范围大,输出误差小,适用于各类扩频通信系统。

An automatic gain control （AGC） circuit used in the intermediate frequency part of the double down conversion superheterodyne receiver front end is introduced. The circuit uses PIN diode ~r networks as electronic attenuators, uses schottky diodes as signal detectors, and uses integrated operational amphfiers to generate the control voltage. Electronic attenuators are distributed in both the first IF part and the second IF part. Measured results show that the proposed automatic gain control circuit has wide control range and low o.utput error for 20MHz bandwidth IF signals so it can be widely used in all kinds of spread spectrum communication systems.