Research On Scattering Characteristics Of The Target Coated With Plasma Sheath By PO Method

When a hypersonic aircraft is flying near space,a plasma sheath will be produced around the aircraft,and the electromagnetic waves will be reflected,absorbed and scattered,thus the scattering characteristics of the aircraft will be changed,and the detection of the aircraft will be affected.Microwave is always used for the traditional radar detection,and it is difficult to penetrate the plasma sheath.Terahertz wave has advantages in the plasma sheath,and it has a wide application prospect in the detection of hypersonic aircraft.Aircraft flying near space,because of the change of flight conditions such as flight speed and altitude,the parameters of plasma sheath are also changing.Therefore,it is necessary to study the scattering characteristics of hypersonic aircraft under different flight conditions.This paper focuses on blunt cone model,thus the bistatic and mono RCS of the model under different conditions of incidence and parameters of plasma sheath are investigated.Based on the simulation data of sheath flow field of hypersonic aircraft,the characteristics of sheath flow field under different flight conditions are analyzed,and the RCS of plasma sheath-coated aircraft in windward and leeward sides at different flight altitudes and velocities is examined.The main works of this paper are as follows:Firstly,concepts related to the calculation of scattering characteristics,such as RCS,PO method and plasma sheath are present,and the plasma sheath is simulated.In addition,the bistatic and mono RCS of the target covered by plasma sheath are calculated by layered method,and the RCS of the target under the different incident angles,different incident frequencies,different polarization modes,as well as different thickness of plasma sheath are compared,thus the difference between different bands in calculating RCS of the target covered by plasma sheath is analyzed.The high resolution range profile(HRRP)is a very important part of the target characteristics.In this paper,the HRRP of the target covered by plasma sheath is calculated,and the HRRP obtained in terahertz band and microwave band under different conditions are compared.The bandwidth of terahertz band is obviously wider than that of microwave band,which objectively provides an advantage and powerful basis for obtaining HRRP of the target covered by plasma sheath in terahertz wave.The flow field of plasma sheath produced by aircraft flying in near space will change with the change of flight conditions.Therefore,based on the simulated non-uniform flow field data of plasma sheath of hypersonic blunt cone aircraft,the temperature distribution and electron density distribution of the flow field at different flight altitudes and velocities are compared and analyzed,and the distribution of electron density perpendicular to the surface of aircraft and the change of dielectric constant with incident wave frequency are calculated.On this basis,The bistatic and mono RCS of the aircraft irradiated directly upon the head and the tail under different flight conditions are calculated,and the numerical results of different incident frequencies and polarization modes are analyzed.