An Improved FDTD Research For Electromagnetic Scattering Characteristics By Complex Cold Plasma

The electromagnetic scattering characteristic of plasma target has an important significance in the field of radar stealth and electronic countermeasures. In recent years, the Finite-Difference Time-Domain(FDTD) method was applied widely among the study of electromagnetic scattering characteristics of plasma target, and many kinds of improved methods have been provided from the constitutive equation of plasma.On the basis of the predecessors, one kind of FDTD method based on the Boris particle model is used for analyzing electromagnetic scattering characteristics of three-dimensional time-invariant plasma in this paper, named the Boris-FDTD method. This approach employs a version of Boris’ s algorithm applied to the particle-in-cell plasma computational models when solving the constitutive equation of plasma. The advantage of this method is that it solves all the equations explicitly and there is no need to calculate Fourier Transform or Laplace Transform of each element of matrix equations, thus it greatly reduces the computation and storage. Firstly, the Boris-FDTD method is used for calculating the Radar Cross Section(RCS) of a collision-less and a collisional plasma ball, and the correctness of the Boris-FDTD algorithm is verified by comparing the results with the results of the Current Density Laplace Transform Finite-Difference Time-Domain(CDLT-FDTD) method and Mie series. Then, the Boris-FDTD method is used for calculating the RCS of a magnetized plasma jet flame missile which proves the Boris-FDTD method has the computing ability to calculate the electromagnetic problem of the actual complex plasma target.However, the plasma parameters of practical applications will change with external objective conditions. More and more practical applications need us to research time-varying plasma model in theory, so the research of plasma from time-invariant to time-varying is necessary. The one-dimensional transient plasma which tends to be the ideal process is researched in this paper. Firstly, an improved FDTD method that can analyze electromagnetic scattering characteristics of one-dimensional transient magnetized plasma and the Modified Nearly Perfectly Matched Layer(M-NPML) absorbing boundary conditions that can truncate one-dimensional transient plasma are deduced by combining with the CDLT-FDTD method of the time-invariant magnetized plasma and the M-NPML theory that can truncate time-invariant plasma. And the validity of the improved method and the absorbing boundary conditions are verified. Then, the improved method is used for researching the effects on frequency-domain characteristics of the electromagnetic wave by the one-dimensional transient plasma. And we found that a suddenly created plasma slab has the effect of frequency shift and new frequency points for electromagnetic wave in the frequency domain.These research results of paper can provide feasible algorithms for analyzing electromagnetic scattering characteristics of time-invariant and time-varying plasma.