Study On Hybrid FDTD Method For Investigating On Interaction Of Electromagnetic Pulses And Typical Strctures On Some Ship Platforms

A large number of antennas and electronic systems equiped on modern shipplatforms will bring a convenience and improvement in communication, navigation,radar and early-warning, while also introduce various unexpected electromagneticcompatibility (EMC) and electromagnetic interference (EMI) problems. As we know,computer modeling and simulation techniques have been successfully adopted andimplemented in predicting the electromagnetic (EM) phenomena and interference.However, how to accuratly predict and quantitatively analyze the effects of thecomplex EM environment using numerical tools on ship platform are still challengesto computational EM researchers. Thus, this dissertation devotes to the EMenvironment effects (E3) and the development of some related hybrid numericalmethods.The major contribution of this dissertation is summarized as follows.(1) The FDTD (2,4) method with low dispersive error is proposed at first inChapter2, and then some related techniques, such as the introduction of plane wavesource, high order near to far field transform technique, and high-order PML aredeveloped based on this method. Besides, both its stability and dispersive error arediscussed in this chapter in details in this chapter.(2) In Chapter2, further studies are focused on a novel FDTD meshing technique,which is based on the CAD model and ray tracing algorithm. There are four steps tofinish the meshing process, which are triangle mesh modeling, intersection pointjudgment, attributes of the intersection judgment and data output. The proposedmeshing technique can surpport both non-conformal and conformal mesh outputs forsolid and surface models.(3) In Chapter3, a FDTD (2,4)-compatible conformal technique to solve curvedPEC objects has been proposed. It has higher accuracy and efficiency than those ofconventional FDTD and FDTD (2,4) methods, as coarse meshes are employed withstaircase errors effectively reduced during its implementation. A rigorous analysis ofits global stability, based on the Fourier method, has been performed and a stabilityimprovement by using user-defined geometric precision technique has been carriedout in this Chapter. At last, this method has been successfully implemented forstudying on shielding effectiveness (SE) of some typical cabin structures andparametric studies have been carried out to show the effects of different EMPs and cabin geometry on SE.(4) A novel high-order interface treatment technique has been proposed forcomputing specific absorption rate (SAR) distribution over the human body model ina metallic cabin illuminated by external EMPs. The proposed method utilizes aneffective dielectric constant to modify the updating equations in the FDTD (2,4)scheme, which is derived by area, linear, and volume average, respectively.Numerical calculations have been further performed to show the average SARdistribution over the human body model for different IEMP incidences by using thearea average concept and good performance can be obtained.(5) A modified hybrid FDTD method, which combines the modified FDTDmethod, the improved theoretical transfer impedance model of shield cable, thin wiremodel, equivalent antenna feed model and MNA method, is presented for computingthe responses of antenna feeding systems inside of an arbitrary cabin. This methodcan provide a co-simulation over the combinational model of field, transmission lineand circuit.(6) A high efficiency parallel FDTD software has been developed for predictingconformal surface current distributions of electrical large platforms such as aircraftsand warships. It has good performance on parallel efficiency and simulationaccuracy due to a new and powerful parallel technique adopted to handle theinformation transform. It has three main parts which are pre-treatment module,FDTD simulation module, and post-treatment module.