A Novel Nonuniform Grid AH FDTD Method for Fine Structure by Using the Coordinate Transformation

This letter proposes an associated hermite finite-difference time-domain (AH FDTD) method suitable for nonuniform grids, which is implemented based on coordinate transformation. A coordinate transformation that can transform nonuniform grids into uniform grids is introduced. Subsequently, by combining the 2-D AH FDTD method with the aforementioned coordinate transformation, a five-point coefficient matrix equation for the electromagnetic field component is obtained. The proposed method is verified by calculating the magnetic field inside a waveguide filled with a lossy medium. The effects of varying different coordinate transformation parameters on the computational accuracy of electromagnetic scattering from metal thin plates with gaps have been investigated. Compared to traditional methods, this method can save computation time while ensuring high computational accuracy when dealing with electromagnetic problems of fine structures. It can also guarantee computational stability even when the ratio of coarse grid size to fine grid size is large.