A Novel Three-Dimensional FDTD Subgridding Method for the Coupling Analysis of Shielded Cavity Excited by Ambient Wave

The finite-difference time-domain (FDTD) method used for the coupling analysis of the shielded cavity usually needs amount of elements, which would seriously affect the computation cost. To relieve this problem, a novel three-dimensional FDTD subgridding method combined with an automesh generator technique is presented. First, the automesh generator technique is applied to read the triangular element data from the stereolithography format file of the shielded cavity to fastly mesh the structure of the cavity by the coarse and fine grids of FDTD. Then, the subgridding interfaces are separated to temporal and spatial parts to implement temporal and spatial subgridding algorithms, respectively, to obtain the electric and magnetic fields on the interfaces. To ensure the stability and continuity of the subgridding interfaces, the missing subgrid and fine grid magnetic fields nearest temporal and spatial subgridding interfaces are obtained by the Taylor expansions and linear interpolation schemes of the coarse grid magnetic fields, respectively, at the end of each fine time step. And the coarse grid electric fields in the subgrid and fine grid nearest temporal and spatial subgridding interfaces should be updated via some interpolation schemes of the subgrid and fine grid electric fields at the end of each coarse time step, respectively. The accuracy, efficiency, and longer time stability of the presented method have been verified by comparing with the finite-integration time-domain method via the simulation of a cavity with one slot excited by the plane wave. Finally, the suitability of this presented method applied for the coupling analysis of the arbitrary shielded cavity excited by the ambient wave is confirmed.