Electromagnetic Properties Based On The Fdtd Method To Analyze A Limited Coplanar Waveguide

As a kind of microwave transmission line with excellent performance and convenient process, the coplanar waveguides (CPW) are increasingly playing greater role in MMIC circuit. Especially in the millimeter wave band, the CPW have the incomparable performance advantages over microstrips. However, the traditional theoretical analysis of CPW are usually based on a series of ideal cases. In order to direct the design of the MMIC circuit better, it is necessary to research on the CPW under the nonideal circumstances. The finite ground's influences on the electromagnetic characteristics of the coplanar waveguides were exactly researched in this paper.In many numerical calculation methods, the FDTD was chose as the research method due to the advantages that the information in very wide frequency spectrum could be obtained by single time-domain calculation. The principles and steps of using FDTD analyzing the coplanar waveguides were presented detailedly in this paper. On the division of grids, the heterogeneous grids were adopted to simulate the field intensity microscopicly and the physical structure precisely. The common excitations and the ways they added were systematically studied. About the treatment of the absorbing boundary, different from the traditional iterative derivation method of directly obtaining the Perfect Match Layer of electric fields by magnetic field, in this paper by introducing the intermediate variable electric flux, the electric flux was computed by using magnetic field and then the electric field was calculated by using electric flux, so that the complexity induced by the various coding in different medium field can be avoided. In addition, eight types of coplanar waveguides with concrete size were given in this paper and their characteristics impedance, propagation constants and effective dielectric constants were calculated. Then the effect rules of finite ground plate on coplanar waveguides were sum up. Finally, the current difficulties of this project were put forward and the prospect of next step work were looked forward to.