Study On Periodic Dispersive Structures Using Split-field FDTD Method

With the fast development of electronic technology and computational ability of computer, the advantage of computational electromagnetism which is interdisciplinary subject analyzing electromagnetic problems is gradually showing. As one of the electromagnetic numerical methods, the finite time domain (FDTD) method is widely used in analysis of complex electromagnetic structures because it can be easily implemented and suitable for parallel processing.The research on electromagnetic characteristics of periodic structures is always the important topic of electromagnetic fields. Periodic structures have been obtained much attention in theoretical research and engineering field for their special characters. For example:the frequency selective surfaces (FSS), photonic crystals (PC) and so on. In recent years, the research on dispersive periodic structures becomes the hot pot, such as asymmetric split-ring slits (SRSs) which have been applied to sensor, and the left hand materials (LHMs) which can be obtained by using the split ring resonators (SRRs), etc. So, it is of vita importance to study the dispersive periodic structures.According to the Floquet theorem, the properties of infinite periodic structures can be obtained through analyzing the single unit by setting the periodic boundary. In the thesis, the split-field FDTD was introduced to solve the problem of oblique incidence on periodic structures. Here, combining with the Z transform method, the split-field method was extended to the study of periodic dispersive structures at oblique incidence.Some contributed works are as follows:Firstly, the background and importance of research of dispersive periodic structures were briefly introduced, and a simple review about the FDTD method was also introduced. Some FDTD methods which were used to simulate the oblique incidence on periodic structures are briefly analyzed.In addition, the foundation of the split-field FDTD method was introduced in detail, and the relevant key technology like the modification of the PML was analyzed. Through the numerical simulation of two dimensional and three dimensional periodic structures, the efficiency of the split field method was demonstrated.At last, combining with the Z transform method, the split-field FDTD method was extended into the study of periodic dispersive structures. The iterative equations of the Drude dispersive model and the Drude Lorentz dispersive model were also provided. Compared with analytical and other numerical results, the efficiency and wide applicability of our method are demonstrated.