Research On High-speed Target Scattering Characteristics And Lidar Phase Modulation Method

Doppler lidar can obtain the speed of moving targets through Doppler shift.With the development of science and technology,Doppler lidar has been applied in many fields such as atmospheric science,transportation life and national defense construction,and it can realize the measurement of high-speed target speed such as high-speed stealth bombers,it has great significance.This paper mainly studies the measurement of highspeed targets as the research background.These two parts are the subsystems of the lidar measurement system,which are the transmitting and receiving system and the frequency discriminating system.Both of these studies are to reserve the technical design for the laser radar measurement system design in practical application.In this paper,we study the scattering characteristics of the target by simulating the Laser Radar Cross Section(LRCS),and obtain the scattering characteristics of different locations of the target by simulation.Firstly,we simulate the LRCS under ideal conditions,and then we simulate the LRCS what is added the shock.We observe the variation of the target lidar scattering cross section with the shock layer,and we observe the influence of the shock wave on the laser radar echo signal power in aero-optics,so as to select the parameters of the radar system in practical applications,such as laser emission power and transmit antenna gain,which lays a theoretical calculation basis for the parameter selection of the whole radar system design.For the research of radar frequency discrimination system,this paper mainly includes the locking research of the working point and the research on the frequency discrimination method-phase modulation method.In terms of laser frequency locking,firstly,we introduce the principle and application of the locking mode briefly,and elaborate the PID control module.Secondly,we improve the experimental optical path,and carry out the corresponding experiment to realize the parameter setting,then we observe and analyze the final locking effect.In the theoretical research of phase modulation method,this paper first introduces the principle of phase modulation method and the frequency discrimination process,and introduces the application of DC term in phase modulation method.Secondly,we introduce the application of normalized amplitude in phase modulation method in detail.The normalized amplitude of in-phase and quadrature components and frequency shift form a three-dimensional curve,and we project it into a two-dimensional curve.Finally,we carry out the MATLAB theory simulation of these methods,and compare the simulation results and solve the problem of insufficient dynamic range of frequency shift measurement.In the experimental research of phase modulation method,firstly,we use the devices in the experiment and introduce related programs based on LabVIEW software briefly,then adjust and improve the experimental light path.Secondly,we carry out the experiment of doppler with the target.The measurement experiment of frequency shift is used to measure the echo signal light,and we compare the experimental results with theoretical the simulation results,and verify the feasibility of the theoretical method.Finally,we carry out the error analysis of the ten sets of frequency shift measurements.The results show that within the range that can be measured by the experiment,the doppler shift measurement error can reach about 1MHz when the position near the ideal working point,most of the measurement error can keep within 2MHz.