Research On Transmission And Scattering Method Of Inhomogeneous Dispersive Medium

FDTD(Finite Difference Time Domain) method is a very important electromagnetic computation method, which solve the differential term based on Maxwell’s equations in a leapfrog way. As a time-domain method, FDTD is widely used in research of transmission and scattering problem of electromagnetic waves in inhomogenous dispersive media.With the deepening awareness of the problem of electromagnetic studies, the spatial dimensions and the complexity of computational model is increasing. Because courant stability condition and numerical dispersion condition have limited the time step and spatial step selection, the usage of time and memory with these complex electromagnetic computation also increases with the number of grid. From this view, this dissertation introduces a non-uniform grid and parallel computing technology in inhomogenous dispersion medium to shorten the computation time and to reduce memory usage.This dissertation describes the important principle of FDTD method, from the incidental signal source, to absorbing boundary like UPML. And through the metal, dielectric, metal- dielectric composite target scattering case to verify the accuracy of the near to far field transformation. For unmagnetized plasma, magnetized plasma, gives a detailed derivation PLRC methods and validated stratification and inhomogenous cases by computing the transmission and scattering properties.Then, for the non-uniform grid method, the dissertation describes the sub-grid method and gentle-changed non-uniform grid. Apply the non-uniform grid method to inhomogenous dispersive medium, and gives a detailed derivation. Then, by solving the scattering properties of double layered and four layered unmagnetized plasma ball, the numerical accuracy of this method is verified. Then after contrast the time and memory consumption with non-uniform method and uniform method, the effectiveness of this non-uniform method is well reflected.Finally, this dissertation describes the parallel computation techniques as MPI method and Open MP method. After a simple comparison of the two methods, a detailed discussion of the Open MP method and its applications in inhomogeneous dispersive media is given. By solving the scattering properties of three layered and five layerd unmagnetized plasma cubic, the numerical accuracy of using Open MP method in inhomogeneous dispersive medium is verified.. Then, through the parallel depth, parallel structure, the three aspects of parallel scheduling, the dissertation separately discussed the way to improve the performance of parallel computation.