Use of the perturbation technique for implementation of surface impedance boundary conditions for the FDTD method

A new approach to implement a surface impedance boundary condition (SIBC) for the FDTD method Is proposed. The explicit FDTD formulation for the boundary cell closest to the surface of a conducting body is obtained using the perturbation technique in the small parameter proportional to the ratio of the values of the electric field at the opposite sides of the cell. The condition of applicability of the technique is obtained. It is shown that an FDTD code where the PEC-condition has been already implemented can be easily upgraded using the proposed technique to take into account properties of the conducting medium and improve accuracy of the computation. Numerical examples are included to illustrate the theory.