Unconditionally Stable FDTD Method for Solving Oblique Incident Plane Wave on Periodic Structures

For solving the problem of the oblique incident plane wave over planar periodic objects, an implicit finite-difference time-domain (FDTD) method is proposed by introducing the Crank-Nicolson (CN) scheme to the field transformation technique. Unlike the previous approaches of field transformation method, this technique does not need to introduce additional field components to handle extra terms and is unconditionally stable as proved by a stability analysis. The accuracy and efficiency of the proposed method is verified by comparing with the split-field method.