Research On Subgrid Techonology For FDTD

As one branch of computational electromagnetic methods, FDTD (Finite-Difference Time-Domain) method is widely used for its simplicity and convenience. This paper is mainly focused on subgrid technology of FDTD method, including Huygens subgrid and Wave-equation subgrid technology for FDTD method.This paper studied on FDTD method, which includes Maxwell equations, absorbing boundary, and accuracy. In the condition of large area with a tiny structure inside, it will costs huge computer storage and computing time to refine all the meshes. Sub-grid technology is applied to promote the meshing efficiency and it is proved to be quite useful. The key problem of sub-grid technology is to calculate the electromagnetic distribution on the interface of coarse mesh and refined mesh accurately. According to the research on subgrid technology, accuracy, stability and arbitrarily ratio steps are attractive advances for subgrid technology of FDTD method.Secondly, this thesis dedicated two subgrid technologies for FDTD method. Wave-equation subgrid technology for FDTD method makes use of wave eqution on the interface of coarse mesh and fine mesh, iterating the electrical component of fine mesh. Huygens subgrid technology for FDTD method uses equivalence principle smartly, connecting two mesh spaces by Huygens surfaces to form one real physical space. There are working region and non-working region for each fictitous space. The introducing of equivalence principle cut down numerical spurious field resulting from the connection of the grids, besides the simulation accuracy is considerable. Furthermore the ratio of the steps can be any odd number, so it is easy to adjust and use.This thesis makes detailed study on Huygens subgrid technology for FDTD, including the basic principles and implementation steps for one-dimensional and two-dimentional cases. Firstly, Huygens subgrid FDTD has been used to simulated normal media.It is adequately verified that the Huygens subgrid method is totally right and also keeps many advantages. Secondly, S-parametert reusults of EBG (Electomagnetic Band Gap) by Huygens subgrid FDTD and by uniform FDTD are in good agreement. Plasma, distinguished from solid, liquid and gas, has many special characteristics. We make analysis about working status of working region and non-working region, by use of connection of Huygens subgrid technology and PLJERC (Piecewise Linear JE Recursive Convolution) FDTD. In two-dimentional situation, reflection from interface of coarse mesh and fine mesh is simulated both in wave-equation subgrid and Huygens subgrid technology, respectively. At last, target RCS (Radar Cross Section) is simulated by two technologies.