Abstract: Necessity for calculating boundary temporary field components in reduced finite-difference time-domain method(R-FDTD) is discussed.A periodic symmetric R-FDTD method is proposed.Temporary components in supplement calculation are given based on symmetry and periodic boundary conditions(PBC).Computational domain is reduced to 1/4 and lateral field components of a symmetry plane are obtained with symmetry relations.Compared with original FDTD,memory storage is reduced to 1/6 while ensuring accuracy. It is shown that the improved algorithm agrees with FDTD method by numerical simulation of EM impulse responses tO infinity wire mesh reinforcement and reinforced concrete layer.The improved algorithm has advantages in saving memory storage and calculation time.

Key words: R-FDTD, FDTD, periodic symmetric structure, reducing optimization