A Novel CDLT-FDTD Investigation For EM Scattering By Plasma And Its M-UPML Absorbing Boundary Condition

In view of the application of the absorption of electromagnetic waves of plasma dispersion medium in various fields and the application of plasma stealth technology, the study of its electromagnetic properties in recent years become a hot topic. The current research methods of its electromagnetic properties are mainly FDTD method. For the FDTD method for electromagnetic scattering by the magnetized plasma, the main difficulty lies in dealing with the dispersive constitutive relation, that is, to deal with the convolution of the constitutive relation from the frequency domain to the time domain.Based on Laplace transform (LT) principle, a new analysis of the dispersion medium of the electromagnetic properties of FDTD algorithm is proposed, called the current density Laplace transform finite-difference time-domain (CDLT-FDTD) algorithm. Making use of the constitutive equation about the current density and electric field intensity vector in the magnetized plasma medium, Laplace transform on both sides of the equations is adopted, respectively, and the constitutive equation in s domain will be attained. At last, by using the inverse Laplace transform over the time domain, combined with exponential difference plan, the FDTD iterative equation in discrete time-domain which are easy to solve can be obtained. There are two advantages of this method. Not only the convolution problem of the constitutive relation of the frequency domain to time domain is avoided by this method, reducing the amount of computation and more memory can be saved, but also it's more suitable for the analysis of engineering problems because the parameters can be more easily controlled in reality.EM scattering characteristic of non-magnetized and magnetized plasma are calculated after the method is validated. The radar scattering cross-sections (RCS) of scattering target are computed while the plasma collision frequency, the plasma frequency and the plasma cyclotron frequency are changed separately. The effect of RCS by parameters of plasma has been analyzed. In the end, the absorbing boundary condition of Modified-UPML algorithm which can truncate dispersive medium is proposed by combining constitutive equation of plasma and Maxwell's equations.The features of this method are making the constitutive equation of plasma be equivalent to current density by taking time-domain to frequency-domain transformation. Meanwhile, permittivity constitutive equation of plasma is used in the normal absorbing boundary condition. Simulation results confirm the validity of this boundary theory.