实现接收机大动态范围的中频AGC电路设计

Design of IF AGC Circuit for Large Dynamic Range Receiver

介绍了AD公司VGA放大器AD8367的主要性能和器件特点,在此基础上,利用其内置检波器构成增益负反馈环路,设计实现了大于75 d B动态范围的中频AGC电路。该电路主要由两级串联AD8367、中间级IF放大器和四级L形宽带电阻匹配网络构成,具有自动调整电路增益以分析强弱差异信号的功能。调试过程中,对信号电平和输入输出匹配电路进行适当调整,以达到AGC电路信号控制范围最大化的目的,最终测试结果表明电路基本能满足接收机系统性能指标的要求。

The VGA device AD8367 of Analog Device is introduced in this paper, including its main performance and device features.On this basis, with its built-in detector to constitute gain negative feedback loop, the IF AGC circuit with more than 75 d B dynamic range is designed and presented. This circuitconsists of two-stage AD8367, middle IF amplifier and four L-shaped broadband resistance matching network, which is capable of automatically adjust overall gain to analyse magnitude diversed signals. During the debugging process, signal level and I/O matching network are chosen carefully to maximize AGC dynamic range. Finally,test results show that this design satisfies receiver requirements, in spite of a little bit distortion.