Study On Key Techniques And Their Applications Of The Finite-Difference Time-Domain Method

As one of the most important methods in electromagnetic numerical simulations, the finite-difference time-domain (FDTD) method has been used to solve many engineering problems successfully. However, the FDTD method can not satisfy the continuous arisen modern engineering requirement better when it is used to deal with more novel and complex electromagnetic problems, so the modified or bran-new FDTD algorithms should be studied. In this thesis, several key techniques of the FDTD method and their applications in electromagnetic problems are studied in depth and detail, the work of the author is mainly focused on:(1). The isotropic frequency-dependent FDTD method based on the lossy Drude dispersive models for left-handed materials (LHMs) is studied. Taking the electric flux density D and the magnetic flux density B as the auxiliary variables, the auxiliary differential equation (ADE) method is used to implement frequency dependence in the FDTD algorithm by combining the constitutive relation between D,(B) and E,(H) with the relation between (?)/(?)t and iω, which can solve the numerical instability. And then the propagation characteristics of the cylindrical wave and the continuous Gaussian beam in isotropic LHMs are studied systematically, which uncovers the electromagnetic characteristics of the LHMs deeply.(2). The conditions that the negative refraction takes place when a plane wave passes from one isotropic right-handed material (RHM) into another biaxial anisotropic left-handed material (BA-LHM) are presented in order to study the negative refraction of anisotropic LHMs constituted by the practicable composite meta-materials. According to the theoretical analysis, several sets of constitutive parameters of BA-LHM are considered, and then the anisotropic frequency-dependent FDTD method based on the lossy Drude dispersive models is presented and used to prove the validities of the theoretical analysis.(3). A novel iteration procedure of a hybrid method combining the method of moments (MoM) and the FDTD method is presented to simulate such a problem involving arbitrarily oriented thin-wire antennas located near inhomogeneous dielectric objects that cannot be resolved conveniently, and/or accurately, by using one single numerical method. The linear antenna is analyzed by MoM and the dielectric objects by FDTD. The scattering field created by FDTD is employed to modify the voltage matrix of MoM. After several iterations, the obtained stable solution will be able to take into account the influence of dielectric objects on linear antenna. Numerical results have a good agreement with those obtained by the software FEKO, which shows that the hybrid method can analyze the performance of antennas near inhomogeneous dielectric objects effectively.(4). A high performance PC cluster is set up that belongs to National Key Laboratory of Microwave and Antennas Technology in China. MPI-based Parallel FDTD method on the PC cluster is realized by subdividing the whole FDTD computation space into several sub-domains and transferring field values across the interfaces between the neighboring processes with three field communication patterns. And then the computation flow of the Parallel FDTD method is presented. Lastly, the general rules are proposed on how to obtain the highest efficiency of Parallel FDTD algorithm by optimizing MPI virtual topology.(5). According to the two conclusions of the optimum virtual topology for MPI-based Parallel FDTD method, in the case of limited computation resources, the three dimensional virtual topology scheme for the Parallel FDTD method is employed to explore its engineering applications, which include scattering characteristics of the through-via in microwave multi-chip module (MMCM) and the PBG microstrip filter, the radiation characteristics of the circular waveguide antenna with PBG high impedance plane, the far field radiation and the near field isolation characteristics of antennas mounted on the electrically large warship and plane, the RCS of the electrically large warship and plane coated a lossy medium.