Finite Difference Time Domain Method For Random Dispersive Media And Its Application

Time domain finite difference(FDTD)is a numerical calculation method of time domain electromagnetic field,which is widely used for its simple principle and wide band information in one calculation.There is a problem of excessive computation when using FDTD method to deal with radio wave propagation of random media.The polynomial chaotic expansion(PCE)FDTD method can characterize the electromagnetic properties of the random media,which is a polynomial expansion of the electromagnetic field value and reduces the stochastic differential equations to a set of deterministic differential equations that can be numerically solved through a simulation.This method is an effective method to solve the electromagnetic problem of random media.In this thesis,the PCE method is introduced into the Bilinear Transform(BT)FDTD method of the dispersive medium.The effects of the random characteristics of the medium in the random dispersive medium on the radio wave propagation are analyzed,and study the radar scattering cross section(RCS)scattering properties of plasma coating targets.The specific contents are as follows.(1)The PCE-BT-FDTD method is proposed and applied to the propagation analysis of the random dispersive media.The statistical characteristics of electric field(including mean value and standard deviation)after plane electromagnetic wave transmitted through a cylinder of random dispersive media are calculated by simulation.Compared with Monte Carlo(MC)method,the correctness and efficiency of the proposed algorithm are verified.The results show that the algorithm not only has the generality for different random dispersive media(Lorentz media,Deby media and plasma),but also avoids the error of correlation coefficient estimation compared with Stochastic FDTD(S-FDTD).(2)The PCE-BT-FDTD method is applied to calculate the RCS of a random plasma coating target.The formulas of RCS based on polynomial chaos expansion are derived.The statistical characteristics of RCS are obtained through a two-dimensional example.Compared with Monte Carlo results,the correctness of the proposed algorithm is verified.(3)Combining bilinear transformation and polynomial chaotic expansion method,the iterative formulas of PCE-BT-FDTD for random magnetized plasma are derived.The statistical characteristics of wave propagation of random magnetized plasma are analyzed.The correctness of the algorithm is verified by a three-dimensional example of random magnetized plasma.