Research On Noise Suppression Technology Of Laser Echo Detection Circuit Based On APD C30927E

Based on pulse semiconductor measuring and tracking laser radar, my Subjectfocuses in-depth research work on improving signal-to-noise ratio and reliability ofecho detection circuit to solve the problem of detecting high-speed, faint echo pulsesignal and eliminating effect of temperature and background radiation on detector. Themain contents include: design of low noise and fast response preamplifier circuit;research on APD temperature drift suppression technology and background light noisesuppression technology.Firstly, low noise and fast response preamplifier circuit design is the key to improvedetection range and ensure ranging accuracy. The low noise design principles aresummarized by analyzing and calculating all kinds of noise carefully according to thecharacteristics of design circuit. The optimum design bandwidth of the system is giventhrough analysis of relationship between bandwidth, stability and noise gain. Finallyexperiments show the circuit can extract the rising time of4.7ns echo pulse signalwithout distortion and make output noise voltage mean square suppressed in hundredsof microvolt.Secondly,to suppress temperature drift of APD on detection performance, this paperdesigns a compensation circuit automatically adjusting APD bias with temperaturechanging according to the relationship between APD bias and temperature when APDgain does not change. Experiments show the circuit can ensure the stability of APD gainbetween0to60degrees by automatically adjusting APD bias.Finally, by analyzing the effect of background light on output signal-to-noise ratio,this paper gets a conclusion that APD optimum gain varies with background light andthen designs a constant noise control circuit automatically adjusting APD bias withbackground light changing. Experiments show constant noise control circuit can keepoutput noise a constant value to ensure the reliability of detection system as thebackground light changes in a day.