基于相敏检波的弱信号检测调理电路设计

摘要

利用相敏检波原理设计一种弱信号检测调理电路.采用射随电路增强驱动能力,并将输入端与后续电路隔离;以PGA870为核心,用单片机编程作控制构成可编程增益放大电路;射随电路、可编程增益控制电路采用差分输入模式提高共模抑制比;根据信号相关性,信号与噪声、噪声与噪声的无关性,采用相敏检波.该功能板能检测到μV和mV级微弱信号,相比单端模式,将共模抑制比提高了7.7dB,增益可在-11.5dB和+20dB之间可调,信号的有效带宽250MHz,输出信号的基波与二次谐波功率比能达到50.8dB.%A weak signal detection circuit is designed by using phase sensitive detection principle.The emitter follower circuit enhances the driving ability,and the input end and subsequent circuit is isolated.By using PGA870 as the core,the programmable gain amplifier circuit is formed as microcontroller programming control emitter follower circuit.Programmable gain control circuit adopts a differential input mode to improve the CMRR.According to the correlation of signal,the independence of signal and noise,noise and noise,it is adopted of the phase sensitive detection.This function board can detect uV and mV weak signal,compared with the single ended mode,it can improve the CMRR 7.7dB,adjust gain between-11.SdB and +20rdB,enable the effective bandwidth of signal to reach 250MHz,and the power ratio of the fundamental wave and two harmonic of output signal to reach 50.8dB.