| As the most widely used passive jammer,chaff plays an extremely important role in electronic countermeasures due to its simple manufacturing,convenient use,and remarkable effects.In order to give full play to the interference effect of chaff in the middle of the ballistic,it is urgent to master Its motion diffusion,electromagnetic scattering,electric wave propagation and other related characteristics in the atmosphere Therefore,the related research on diffusion model of chaff cloud and electromagnetic scattering characteristics has gradually become a topic of great interest to researchers engaged in target characteristics at home and abroad.This thesis focuses on chaff cloud clusters,and mainly conducts research in two directions.On the one hand,it analyzes the movement state of chaff in the atmosphere in depth,and gives the motion equations of chaff translation and micro-movement,So as to get the movement diffusion model of chaff cloud;on the other hand,the electromagnetic scattering characteristics of the chaff cloud cluster are studied,including the dynamic RCS simulation of the chaff cloud,the Doppler frequency shift derivation caused by the chaff micro-motion,and the cloud Radar echo model simulation and the study of the second-order statistical characteristics of the echo,the main work of the full text is as follows:1.Simulate the movement and diffusion model of chaff clouds.This paper uses the theory of low Reynolds number flow to analyze the atmospheric environment in which chaff moves.By linearly fitting the air density and air viscosity coefficient data in the standard atmosphere,obtained the general expressions of air density and air viscosity coefficient changing with altitude,the dynamic characteristics of a single chaff are analyzed,and the force and motion equation of a single chaff are given.Based on DSMC(Direct Simulation Monte-Carlo)’s chaff cloud motion diffusion model simulation method,using statistical principles to define the initial position and orientation of the chaff in the cloud,so as to obtain a series of results of the chaff cloud diffusion under different conditions,and the foil at different times quantitative analysis was made on the state of chaff cloud.2.The dynamic RCS of the chaff cloud cluster over time is simulated by simulation.According to the position and orientation of the chaff at different times,this paper uses the octree algorithm to divide the chaff cloud into several sub-blocks,and uses the GEC method to divide each sub-block.Chaff distributed in any azimuth is regarded as a homogeneous medium,and the RCS of the homogeneous medium is calculated,and then the dynamic RCS of the cloud is obtained by superposition.Then the Mueller matrix is used to characterize the variable polarization effect of the chaff cloud.Based on the Mueller matrix,the polarization degree,co-polarization and cross-polarization RCS extreme values of the uniformly oriented chaff cloud are studied.3.Simulate the radar echo model of the chaff cloud,analyzed the Doppler effect caused by the micro-movement of the chaff,and obtained the radar echo of the chaff cloud through the method of multi-point echo vector synthesis.analyzed the influence of chaff cloud angular velocity on power spectral density(PSD)broadening.4.Analyzed the influence of chaff cloud on the echo correlation of cloud,derived the full polarization power spectrum of the chaff cloud,and simulated the echo power spectrum of the uniformly oriented chaff cloud at different angular velocities.Analyzed the effects of different angular velocities on the echo power spectrum of chaff clouds under different polarization modes are discussed. |
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