Study On High Frequency Methods For Electrically Large Scatterers

Study on the electromagnetic characteristic of electrically large scatterers is becoming more and more important in recent years. The application of traditional low frequency methods such as method of moment, finite element method are limited because of the limited computer memory and CPU. While high frequency asymptotic methods are fast and usually require very small computer memory. They are important methods for analyzing the electromagnetic properties of electrically large scatterers.In this thesis, some popular high frequency algorithms, such as the geometrical optics, physical optics and the equivalent edge current method, are reviewed, including their recent developments and applications in analyzing electrically large scatterers. First geometrical optics algorithm is used to calculate the radar cross sections of electrically large scatterers, where at the edges, the algorithm is modified with uniform geometrical theory of diffraction. The electromagnetic characteristics of a group of scatterers are analyzed using physical optics, and the numerical results are compared with the simulation results using commercial simulation tools. Electrically large perfect electric conductor(PEC) plates are analyzed using equivalent electric and magnetic currents, where equivalent edge currents are calculated to account for the mutual electromagnetic coupling between adjacent PEC plates. Meanwhile, the hybrid method that combining the high frequency asymptotic methods with the generalized transition matrix method is also discussed. Numerical examples show that the hybrid method is very fast and can provide adequate numerical accuracy.