Study On Electromagnetic Scattering Characteristics Of Plasma Coated Targets

During the process of the space hypersonic vehicle re-entering into the atmosphere,a complex plasma sheath will be formed on the surface and surrounding space.The existence of the sheath will have a serious impact on the electromagnetic wave,which not only restricts the development of the hypersonic vehicle but also makes it difficult to detect and identify such targets.Therefore,it is necessary to comprehensively and systematically study the electromagnetic scattering characteristics of the plasma sheath coating targets.However,flight tests and ground tests are limited by many conditions,the measured data is expensive to obtain.Therefore,it is an economical and easy method to simulate the electromagnetic scattering characteristics of the coated targets.Based on the radar echo simulation of the plasma sheath coated target,the electromagnetic scattering characteristics of the plasma sheath coated targets are analyzed by using one-dimensional distance image and two-dimensional imaging results.The specific work is as follows:Firstly,the interaction between plasma and electromagnetic waves is discussed.Based on the high frequency physical optics(PO)method,the radar echo of the plasma sheath enveloped target is modeled and simulated.Based on the introduction of the targets motion state and several plasma variation laws in the reentry process,the current commonly used model is used to set geometrically models of the target and the coated plasma sheath.The PO algorithm is used to calculate the RCS of the target,and the echo phase of the target is calculated by combining the dynamic characterization of the target and the estimation of the influence of the plasma on the phase.According to the principle of echo signal generation,the simulation of the sheath and echo of the target sheath are realized.Secondly,the electromagnetic scattering characteristics of the plasma coated target in the high temperature vacuum chamber environment are analyzed,including RCS attenuation and scattering center distribution.The high temperature vacuum cavity environment and one-dimensional distance image and two-dimensional imaging algorithm based on step frequency are introduced.The radar echoes of sheath-covered targets under different plasma parameters are simulated.The effect of the sheath on the distribution of the target scattering center is analyzed by two-dimensional imaging results,the effect of the sheath on the RCS is analyzde by one-dimensional distance image.Finally,based on the results of ISAR imaging,the electromagnetic scattering characteristics of the reentry radar target are studied and analyzed.The motion characteristics of the reentry segment and the principle of ISAR imaging are introduced.Taking the reentry bullet as an example,the effects of plasma sheath parameters and the effect on the target ISAR imaging results are analyzed according to different flight states.