Time Domain Analysis Of Electromagnetic Scattering Characteristics Of Large Target

Recently, with the development of short-pulse (broad-band) communication and radar systems, the time-domain numerical techniques of transient electromagnetic scattering have attracted extensive attentions. In particular, the time-domain versions of various frequency-domain high-frequency techiuques applied to perfectly electrically conducting (PEC) targets have been developed greatly. Compared with time-domain low-frequency methods (such as FDTD, TD-FEM, TD-MoM), time-domain high-frequency techniques require less computer memory and simulation time. This thesis briefly introduces the high frequency techniques, such as Physical optics (PO), equivalent edge currents (EEC) and shooting and bouncing rays (SBR) at the begining of each chapter, and then focuses the main efforts on the researches of the corresponding time-domain versions of these high frequency techniques.The main contributions of this thesis are listed as follows: Firstly, the expressions of time-domain Physical optics (TDPO) are derived from the expressions of PO through the Fourier inversion, and the basic theories of PO method are also summarized. Secondly, the expressions of time domain equivalent edge currents (TDEEC) are derived from the expressions of EEC through the Fourier inversion, and the basic formulations of EEC method are also introduced. The scattering field of TDPO is corrected effectively through the time-domain diffracted field of edge computed by TDEEC and the accuracy of TDPO is improved. Thirdly, TDSBR is studied to calculate the electromagnetic scattering arising from multiple bounces. Finally, RCS of target coated with radar absorbing material (RAM) is studied and analyzed by high frequency mehods. Numerical results demonstrate the accuracy and efficiency of frequency-domain and time-domain high frequency methods discussed in this thesis.