Research On Time-domain Electromagnetic Scattering Of Chaff Cloud Based On Transient Vector Radiative Transfer Theory

Chaff cloud is mainly used in the field of Passive Jamming countermeasure,and it is one of the most widely used target shielding methods in the sea battlefield and air battlefield.The target releases a large number of metal foils in the air,so that the enemy radar can receive the composite scattering echo of the target and the jamming object at the same time,which will cause the erroneous judgement of the target characteristics by the seeker,so as to improve the survival rate of our military target.In Passive Jamming,chaff has the advantages of low cost,high universality and no need to know enemy radar information in advance.In order to better study the tactical use of chaff cloud,it is necessary to study the time-domain electromagnetic scattering characteristics of chaff cloud under different diffusion conditions,and evaluate the effectiveness of chaff interference on this basis.In computational electromagnetics,chaff cloud is composed of large-scale randomly distributed chaff,and chaff is a scattering object with small electrical size.The electromagnetic coupling between chaff is strong,which makes the electromagnetic scattering calculation of chaff cloud face great pressure.In order to give a strategy to quickly calculate the time-domain electromagnetic scattering echo of chaff cloud,this paper first establishes the geometric model of chaff cloud under different diffusion conditions based on aerodynamic principle.On this basis,the scattering echo of chaff cloud under the excitation of modulated Gaussian pulse is obtained based on the TVRT theory and MCM.The interference efficiency of chaff cloud is evaluated based on the calculated time-domain echo.In order to verify the reliability of the algorithm in this paper,a self-developed chaff cloud time-domain scattering measurement system is built in the laboratory to realize the controllable time-domain electromagnetic scattering measurement experiment for chaff cloud.Firstly,analyze the movement law of a single chaff based on random dynamics,and then analyze the influence of the launch angle on the movement trajectory of the chaff projectile.According to the force analysis results of a single chaff,the overall movement characteristics of the chaff cloud under different diffusion conditions are studied,and finally the geometric contour of the chaff cloud,the position of the chaff,and the direction of the chaff over time are obtained.And the chaff cloud diffusion model affected by wind at slow time is obtained.Secondly,to explore the effective research method of chaff cloud time-domain scattering mechanism—TVRT theory,and use the MCM-based "photon collision method" to solve the TVRT equation.In order to increase the applicability of this method,the principles of time translation and SSP are introduced.Thirdly,the TVRT theory and MCM are used to study the time-domain electromagnetic scattering of chaff clouds.In order to comply with the radar's working system,this paper selects the modulated Gaussian pulse to excite the chaff cloud,and considers the nonuniform illumination characteristics caused by the transmitting antenna pattern.Before conducting time-domain electromagnetic scattering research,the chaff cloud was partitioned in three-dimensional space according to the spatial distribution density of the chaff.The Mo M is used to calculate the electromagnetic transmission coefficients of each zone one by one to obtain accurate three-dimensional electrical parameters of the chaff cloud.At the same time,in order to speed up the calculation,this paper studies the principle of time translation and superposition.The simulation results show that under the condition of unilateral modulated Gaussian pulse excitation,the chaff cloud scattering echo has multiple peaks,which is caused by the existence of multiple equivalent scattering centers in different spatial positions of the chaff cloud.In the time domain,chaff clouds with larger sizes have more scattered echo peaks,and chaff clouds with higher density have denser equivalent scattering centers.Therefore,different geometric contours and spatial number density distribution have a greater impact on the echo of chaff cloud.Finally,the self-developed indoor time-domain measurement system is used to measure the scattered echoes of chaff clouds under short pulse excitation,and the echoes of different shapes of chaff clouds under quasi-static conditions are obtained to verify the credibility of the algorithm in this paper.Increase the system signal-to-noise ratio by clutter suppression,time-domain windowing,pulse accumulation and other methods.In terms of making the physical model of chaff cloud,this paper proposes to use the strategy of "low-scattering foam material + imitation metal chaff wire" to establish a static model of chaff cloud,and complete the internal field time-domain scattering experiment based on this model.