Reduction of late time instabilities of the finite-difference time-domain method in curvilinear co-ordinates

Late time instabilities are always present when applying the finite-difference time-domain (FDTD) method in general curvilinear coordinates. Stability analysis is performed on local nonorthogonal FDTD (LNFDTD) and the result indicates that the source of numerical instability is due to the inherent dissatisfaction of the divergence-free condition for the electric field in a source-free space. An efficient ´time subgridding´ scheme is proposed to reduce instabilities so that the full characteristics of electromagnetic structures can be explored. Numerical simulation based on the proposed scheme shows good agreement with theoretical prediction.