An Anomaly Suppression Method Of Radar On Plasma-sheath-covered Reentry Vehicles

Reentry vehicle is an important engine leading the development of space science and technology.Its potential military value and huge strategic advantages have attracted the wide attention of science and technology powers in the world.When the reentry vehicle is flying at a velocity close to the limit in the atmosphere,the high-velocity incoming flow penetrates the shock layer and generates dynamic potential energy conversion.All kinds of gas molecules are dissociated and ionized under the influence of aerothermal,and a layer of high-velocity electromagnetic fluid composed of a large number of charged particles,namely plasma sheath,is formed on the surface of the reentry vehicle.As the plasma sheath is a complex electromagnetic medium,it produces amplitude,phase and frequency complex modulation effect on electromagnetic wave,resulting in abnormal electromagnetic characteristics of the reentry vehicle and forming a "fluid-structure coupling target" of fluid covered rigid body.When conducting radar detection of reentry vehicle in the environment of plasma sheath,a series of electromagnetic coupling effects between plasma sheath and radar signal are generated,which makes the existing radar signal processing methods ineffective,and the one-dimensional range profile of echo produces "interference target",which seriously affects the reliable detection of reentry vehicle in near space.Aiming at the problem of radar detection anomaly of reentry vehicle caused by plasma sheath,this paper aims to propose a method to effectively suppress the interference target of one-dimensional range profile of reentry vehicle echo in the environment of plasma sheath.Based on the numerical results of the flow field of a typical RAM-C reentry vehicle,the electromagnetic reflection mechanism of the fluid-structure coupling target was studied by improving the equivalent wave impedance method.The multi-domain feature mapping model of the radar echo of the reentry vehicle in the plasma sheath environment was solved,and the mechanism of interference of the one-dimensional range profile of the echo signal was revealed.An equivalent time-delay estimation-declining intra-pulse Doppler frequency extraction method was proposed,and the interference targets of one-dimensional range profiles were effectively suppressed by multi-channel parallel compensation-filtering.The multiperiod radar echo inter-pulse coherent accumulation model is derived,and an inter-pulse energy focusing method is proposed to adapt to the steady state/time varying state of plasma-sheath-covered targets.The main innovations and research contents of this paper are as follows:1.The electromagnetic reflection mechanism of the fluid-structure coupling target is studied.Based on the improved equivalent wave impedance method,the spatial distribution characteristics of electromagnetic wave reflection intensity in the heterogeneous plasma are studied,and various electromagnetic effects of the heterogeneous plasma coating metal medium are obtained.Based on the numerical results of the flow field of a typical RAM-C reentry vehicle,the electromagnetic shielding characteristics of the fluid-structure coupling target were analyzed,and the reflected frequency migration characteristics of high velocity electromagnetic fluid were studied.2.Revealed the mechanism of interference targets: According to the electromagnetic reflection mechanism of the plasma-sheath-covered target,the time domain characterization of radar echo was solved,and the multi-domain mapping model of the plasma-sheath-covered target echo signal was established.By comparing the theoretical calculated values of each domain with the actual simulated values,the generation mechanism of interference targets in the plasma sheath environment was revealed.Based on the historical measurement data of typical reentry vehicle shrinkage model under ballistic target,the generation mechanism of jamming target is equivalent verified.3.The suppression method of one-dimensional range image interference of radar echo of reentry vehicle in the plasma sheath environment is proposed: According to the interference mechanism of one-dimensional range image of plasma sheath-coated target radar echo,an equivalent time-delay-deskew method of intrapulse Doppler frequency extraction was proposed,multi-channel parallel compensation-filter processing was carried out on the echo signal,and energy focusing technology was used to improve the energy gain of the true target,so as to effectively suppress the interference target.According to the processing results of jamming targets under typical flight conditions and radar parameters,the suppression performance of the proposed algorithm is evaluated.4.Realized the inter-pulse energy focus of multi-period radar echo of the reentry vehicle in the plasma sheath environment: Based on the space motion geometry model of the reentry vehicle and the space-time transformation model of electron density,the inter-pulse coherent model of the stationary/time-varying plasma sheath coated target was established,and the effects of intra-pulse Doppler frequency,inter-pulse Doppler frequency and time-varying complex reflection coefficient on the inter-pulse coherent property of multi-period radar echoes were studied.In order to achieve effective energy focusing of multi-period echo signals,an interpulse energy focusing method is proposed in the steady-state/time-varying plasma sheath environment.In summary,this paper studies the detection problem of reentry vehicle in the plasma sheath environment,reveals the abnormal detection mechanism of plasma-sheath-covered targets,and proposes corresponding suppression processing technology to achieve effective detection of real targets.The research results have important guiding significance for realizing reliable early warning detection and robust tracking of plasma-sheath-covered targets.