基于FDTD算法的表面阻抗吸收边界的研究

Study on surface impedance absorption boundary based on FDTD algorithm

摘要:

吸收边界条件是时域有限差分(FDTD)算法解决电磁计算问题的一种重要条件。对4种吸收边界方法：卷积完美匹配层(CPML)、表面阻抗吸收边界条件(SIBC)和2种媒介吸收体的原理进行推导，通过Matlab软件对FDTD算法进行编程计算。将4种方法用于微带低通滤波器和分支耦合器2个微带结构中，计算其反射系数。通过改变空气层厚度和迭代步长，4种方法均能得到正确的结果。对比分析4种吸收边界方法在2个模型中的计算时间、内存占用、误差百分比，可知SIBC占用内存最少，计算效率更高，误差百分比为1.63%。

Abstract:

Absorption boundary condition is an important condition for solving electromagnetic computing problem by Finite Difference Time Domain(FDTD) algorithm. First of all, four absorption boundary methods are selected, and the principles of Convolution Perfectly Matched Layer(CPML), Surface Impedance Boundary Conditions(SIBC) and the absorbers are derived respectively; FDTD algorithm is programmed and calculated by Matlab software. Then, the four methods are applied to two microstrip structures, the low-pass filter and the branch coupler, and the reflection coefficient is calculated. By changing the thickness of the air layer and the iteration step size, the four methods can get the correct results. Finally, the results of the two models are compared and analyzed in terms of computing time, memory usage and percentage of error. Compared to other absorption methods, SIBC has the least memory usage, higher computational efficiency, and an error percentage of 1.63%.