Abstract: The total-field/scattered-field technique of the incident wave introduced into the total field region is dealt with for alternative direction implicit finite-difference time-domain method. By observing the grid points at the vicinity of connecting boundary for the two-dimensional TM wave, the incident wave field components should be added in each sub time step. Based on the computational formulations and the particular location of grid points at or near the connecting boundary, there are 14 cases to be considered, including 10 cases for electric field grid points. This technique inherits the characteristics for the introduction of the incident wave in the conventional FDTD method. The solution to linear system equations in this technique is also consistent with that in the ADI-FDTD method. It is demonstrated that the plane wave can be successfully introduced into the total field region by this technique, even when the time step size is 4 times longer than that of the Courant-Friedrich-Levy limit. Finally, the radar cross sections for a conducting column and an airfoil coated with a lossy medium is computed, showing the feasibility of the proposed technique.

Key words: electromagnetic scattering, ADI-FDTD method, total-field/scattered-field technique, radar cross section