Efficient mesh truncation techniques for the solution of Maxwell's equations using the finite-difference time domain method.

摘要

The application of the Finite Difference Time Domain (FDTD) method to open region radiation problems requires the truncation of the infinite domain down to a finite-sized domain amenable to numerical simulation. The accuracy of the solution and the computational expense required to attain the solution are dependent on the method used to simulate the infinite domain. The Berenger perfectly matched layer (PML) technique is shown to offer the potential for near reflectionless absorption of propagating waves at the expense of additional layers of absorbing material with twice the number of unknowns as in the interior domain. However, since the PML allows the buffer region between the discontinuity and the termination plane to be reduced, the overall computation time for a given accuracy level may be significantly reduced.; An efficient reduced field implementation of the Berenger perfectly matched layer concept is developed for regions where there is one nonzero conductivity component. The split-field components in the PML are reduced to the original six field components and two additional auxiliary variables that represent time-dependent sources. Combination of the reduced field formulation in the wall regions with the split formulation in the edges and corners results in an efficient PML algorithm. Memory and CPU time requirements may be reduced by up to one-third without loss of accuracy.; The evanescent PML modification for the split-field PML is shown to apply to the unsplit formulation for a particular choice of the PML material parameters. A lossy modified PML formulation similar to the generalized PML is also presented.; The modified PML formulation is applied to the analysis of inhomogeneous antenna structures. Numerical studies are performed to determine general PML parameter guidelines required for accurate calculation of far-field radiation patterns and input impedance. The PML is also applied to the problem of near-field characterization of antennas radiating in the presence of biological bodies.