Towards the Stable FDTD Subgridding Method with SBP-SAT Technique and Arbitrary Grid Ratio

A provably stable summation-by-parts simultaneous approximation term (SBP-SAT) finite-difference time-domain (FDTD) subgridding method with arbitrary grid ratios is proposed to solve the transverse magnetic (TM) problems efficiently. The SBP-SAT technique and the carefully designed interpolation matrix with the grid ratio 1:n are used to guarantee long-time stability and accuracy. By introducing a virtual intermediate domain, the interpolation matrix with an arbitrary grid ratio is derived, which is flexible to model complex structures. Numer-ical results show the accuracy, efficiency and flexibility of the proposed subgridding method.