总场-散射场方法在二维ADI-FDTD中的实现

提出了一种新的交替方向隐式时域有限差分激励源加入的总场-散射场方法．在总场边界附近，二维TM波的电磁场格点在每个子时间步都需要加入入射波的相应分量．根据交替方向隐式时域有限差分迭代公式及格点在总场边界的具体位置共有14种情况需要修正，其中电场格点有10种情况．该方法继承了常规时域有限差分加源的特点，而且保持了交替方向隐式时域有限差分求解线性方程组的形式不变．在入射波为平面波时，计算表明，当计算时间步长为Courant-Friedrich-Levy稳定性条件所限制时间步长的5倍时，总场区的入射波仍具有很好的场量等值线．利用该方法给出的金属方柱和前端有介质涂层的复杂目标金属机翼散射的数值计算结果验证了其有效性．

Implementation of the total-field/scattered-field technique in the 2D ADI-FDTD

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.