Study Of Application Of Moving Coordinate FDTD Method On Electromagnetic Pulses Propagation

Finite-Difference Time-Domain (FDTD) method is widely used in electromagnetic simulation. Because FDTD method is a full-wave method, when simulating propagation of electromagnetic pulses over long distance, the computational burden quickly becomes too large. That is the major difficulty why FDTD method can not be applied to simulating long distance propagation of pulses directly. When using moving coordinate frame FDTD method, the coordinate system is'frozen'with pulses, and pulses are in small calculation zones when simulating. The FDTD meshes (in the dimension along the propagation path) need only to be large enough to contain the pulses while using this method to simulate propagation of pulses. The application of moving coordinate frame FDTD in propagation of pulses is studied in this dissertation.Firstly, the types of electromagnetic pulses and the current studies of numerical simulation of EMP propagation are introduced. Then, FDTD method and the difficulties in simulating the propagation of pulses over long distance using FDTD method directly are introduced. In order to overcome these difficulties, moving coordinate frame FDTD method are developed. And, the stability and numerical dispersion of this method in one dimension are studied, stability condition is deduced and the results show that moving coordinate frame FDTD method in one dimension is free of numerical dispersion. Simulation results of homogeneous and inhomogeneous media using both FDTD and moving coordinate frame FDTD are compared, the advantage of moving coordinate frame FDTD is validated. This method is extended to three dimension case. The discretized form of moving coordinate frame FDTD in three dimensions is given, and is used in propagation of waves of different frequencies in a rectangular waveguide. After comparing the results of both FDTD and moving coordinate frame FDTD, this method is numerically validated.The feasibility of moving coordinate FDTD are proved In this dissertation. This method can be widely used for simulating propagation of electromagnetic pulses.