A Hybrid FDTD Algorithm without the Limitation of CFL Condition

Aiming at the problem that it is difficult to calculate large-scale matrix eigenvalues in explicit unconditionally stable FDTD algorithm, a hybrid FDTD algorithm without the limitation of CFL condition is developed. This algorithm is based on the explicit unconditionally stable algorithm, which reduces the matrix size by mixing with the traditional FDTD. The hybrid algorithm makes the calculation of eigenvalues only in the fine mesh and the coarse mesh around the fine mesh, which greatly improves the calculation efficiency.