Auxiliary Field Fdtd Method And Its Application In The Analysis Of Planar Periodic Structure Of The Electromagnetic Characteristics,

This thesis is devoted to the theory and the application of the auxiliary fields Finite-Difference Time-Domain (FDTD), which is an analytic method of the electromagnetic properties of infinite planar periodic structures.First, the fundamental theory of the basic FDTD method and its application in the analysis of the electromagnetic properties of infinite planar periodic structures is summarized. The basic ideas of the auxiliary fields FDTD method is expressed and generalized to the situations of the 2-D periodic structures, to lossy media, and to the curvilinear coordinate. The shortcoming of this method in the management of conformal grids is pointed out. Expressions in three kinds of perfectly matched layer (PML) absorbing boundary conditions is also given.Second, the numerical theories of the auxiliary fields FDTD method is studied, including the stability of the differential equations and the numerical dispersive relationship. The stability of two kinds of differential formulations and three kinds of PML is compared, using a straight method depending on the pmax-t graph.Based on the fore-mentioned theory, several typical kinds of periodic structures are analyzed using the auxiliary fields FDTD method. Some frequency selecting surfaces (FSS) are studied as the examples of the structure without source. Waveguide aperture phased array antenna is analyzed using the transparent source technique and the auxiliary fields FDTD. A method to calculate triangular lattice array is put forward. Then, the auxiliary fields FDTD is used to the periodic structure made of dispersive material, such as the pyramid absorbers in anechoic chamber. The permittivity vs frequency property of the absorber is approached by some dispersive equation model, such as Debye model and Lorentz model, so the broadband response of the absorber can be gotten through one calculation. As another aspect of the applications of this method , the scatted electromagnetic field of the fractal rough surface is analyzed, and the relationship between the fractal dimension and the pattern of the scattering coefficient is summarized.