Laser Transient Echo Signal Phase-locked Detection Technology

Light screen and sky screen are commonly used in the range test, these devices are expensive, complex structures and difficult operation and other inadequate, meanwhile, there test accuracy is not high enough. Therefore, a high precision and easy to be operated device is urgently needed in the range test. Active photoelectric target (using the reflection principle for target detection) has it’s own advantages, many scholars are exploring and researching on it, however, the reflected echo signal of the device is very weak or even submerged in noise in the high speed moving target detection, causing the insufficient of the output SNR, Which limits its applications. For problems of this active photoelectric target, this thesis uses correlation detection principle, designed a new type of lock detection circuit, which improved the output SNR, increased the active photoelectric target detection area, can real time detect reflected of the dynamic target echo signals.Through access to relevant weak signal detection methods and literature, combined with the actual needs of this subject. lock detection circuit is designed to detect and extract the effective projectile signal. Research and analysis the projectile signal and its characteristic through theoretical demonstration and the overall design of the experimental program, Choose appropriate a semiconductor laser and high frequency response APD photodetector. Using Labview software simulation of modulated laser light and non-modulated laser light impact on test results, the result of modulated laser light is better, and as a theoretical basis, design the overall circuit, including laser modulation circuit, APD power supply circuit, transimpedance amplifier circuit, filter circuit, and the subsequent lock-in amplifier processing circuit. The design of the circuit has a high bandwidth and good output SNR, after simulation experiments, obtained the required projectile signal. Through software simulation analysis and related experiments, the design of the circuit effectively inhibite interference noise, projectile signal can be detected and extracted from the noise, achieved ideal projectile signal after processed, consistent with the theoretical analysis, this technology effectively solves the active photoelectric target output SNR shortage, provide technical reference for the development of new active photoelectric target.