Research Of Cfdtd-mpstd Hybrid Algorithm

There are three different types of structure in typical computational electromagnetic problems: the electrical fine structure, the wavelength comparable structure and the electrical large-scale structure. These three types of structure are often included in one problem simultaneously with which it is very difficult to deal by one single time domain full-wave algorithm. It is very difficult to select the algorithm which can be an optimization with both modeling accuracy and efficiency: if grid is in accordance with the fine structure, the storage will increase dramatically, and the computational rate will become very slow; but if the efficiency is emphasized, it will make the fine structure neglected unproperly and it will deteriorate the accuracy. Among the Time-Domain Full-Wave algorithms on electromagnetics, conformal finite difference time domain method (CFDTD) is accurate and flexible to deal with the fine structure, but multidomain pseudospectral time-domain method (MPSTD) gets a good performance in the analysis of electrical large structure. In order to analyze the electrical large and multi-scale structure, a hybrid algorithm named CFDTD-MPSTD is developed combining the advantages of these two algorithms in this paper, which makes a balance between the electrical fine and large structure. The subregions divided are solved independently, and the upwind boundary conditions are used to transfer and change the fields in the algorithm. The numerical results demonstrate that the hybrid algorithm can analyze multi-scale electromagnetic problems efficiently.The related technology of CFDTD-MPSTD algorithm is studied in detail in this paper, the main work is described briefly as follows:(1) In order to reduce the grid error in the general FDTD, the conformal grid technology is systematically studied to analyze perfect electrical conductor ,dielectric surfaces and dielectric coated surfaces.(2) The automatic conformal grid generating technology based on automatic conformal meshing is emphasized which gets the intersect points by projection, and the availability of this method is demonstrated by certain examples.(3) The algorithm of MPSTD is systematically introduced in this paper.The methods based on Chebyshev-Gauss-Lobatto(CGL) points and Legendre-Gauss- Lobatto(LGL) points of the collocation method are both discussed, the Maxwell equations are rederived under the curvilinear coordinate system in detail, and subdomain boundary matching conditions on the interface are studied thoroughly.(4) The CFDTD-MPSTD hybrid algorithm is proposed to meet the need of multi-scale electromagnetic modeling. Firstly, the CFDTD subdomain and MPSTD subdomain are solved independently by updating the field; then the field is exchanged and transferred on the interface of different regions by modifying the tangential field using upwind boundary conditions. Finally, the field is updated forward at the time domain using the multiple time step method.