Research On High Sampling Rate Lidar Detection Technology Based On Waveform Measurement

With the development of lidar technology,the jamming technology of lidar is becoming more and more abundant.How to ensure the effective detection effect of lidar in the jamming environment has become the current research hotspot.Laser active jamming technology can deceive lidar by imitating or changing target echo signal.The conventional lidar can only sense the rising edge or falling edge of the target signal,which is limited in the complex photoelectric jamming environment.In addition,when the lidar detects the target,it often meets the situation that the enemy equipment is small and the conventional lidar is difficult to detect it.However,for the small target equipped with optical detection system,under the irradiation of laser beam,the echo signal on the imaging optical system will be produced several times stronger than the diffuse reflection,which is called "cat-eye effect".In view of these situations,this project studies how to use cat-eye effect to improve the ability of lidar to detect small targets with photoelectric system.At the same time,it develops a full waveform detection lidar technology which is different from the conventional lidar signal response mode,so as to realize the effective detection of the enemy's photoelectric detection system in complex noise and interference environment.According to the design requirements of "cat-eye" target,high frequency sampling and Lidar based on waveform measurement,this paper proposes a design of lidar control system with high sampling rate based on waveform measurement.Through high bandwidth signal processing circuit and high frequency sampling full waveform acquisition technology,the waveform of lidar echo signal is outlined,and the restored waveform is analyzed.In this way,the anti-jamming ability of lidar is improved and the effective detection of targets in complex jamming environment is realized.An experimental system based on STM32 embedded ADC sampling for target tracking is constructed.The system mainly includes STM32 control core,scanning galvanometer module,APD receiving module and signal processing circuit.STM32F103ZET6 is used as the control core of the lidar experimental system based on waveform measurement.The galvanometer module adopts CTI 6210 H galvanometer and corresponding drive motor and servo board,which is controlled by DAC8563 digital to analog conversion module.Avalanche photodiode(APD)is used in the photodetector,followed by signal processing circuit to filter and amplify the signal.The circuit design includes lmh6629 transimpedance amplifier and ADA4927 voltage amplifier,and the analog-to-digital conversion circuit adopts PCLE4616 high-speed acquisition card,which can achieve 1GHz sampling frequency.At the same time,the host computer and the acquisition card have fast data transmission speed through PCLE3.0 interface.The experimental system can return the echo waveform of the target to the host computer and realize the restoration of the waveform.In the experiment,the reflector is used to simulate the "cat's eye" target,and the spiral scanning method is used for sampling to realize the tracking of the close range target and the detection of the target contour.On the basis of the experimental system,this paper calculates and analyzes the coordinate relationship between the rotation angle of the double scanning galvanometer and the points on the scanning plane,and studies the accuracy and stability of the galvanometer module.Based on the test of the experimental system,a lidar prototype based on waveform measurement is developed.At 1GHz sampling frequency,the system noise test,longdistance fixed point echo waveform receiving test and ranging experiment test are carried out.The echo waveform of 100 meters target is restored,and the single pulse ranging is realized on the basis of waveform measurement.Different from the conventional pulse laser ranging,the pulse laser ranging of the prototype is less limited by the laser pulse width.