FDTD method for scattering parameters extraction of rectangular waveguide loaded with anisotropic dielectric material

In this paper, three-dimension (3D) finite-difference time-domain (FDTD) method is proposed to extract the scattering parameters of anisotropic dielectric material loaded on a rectangular waveguide. Here, the scattering parameters, i.e. reflection coefficient (S₁₁) and transmission coefficient (S₂₁), are extracted from the electric fields obtained on different observation planes closed to the material. The principal used to analyze electromagnetics (EM) wave scattering based on FDTD method is a wave orthogonality and discontinuity which occurs inside the rectangular waveguide. To validate the result of FDTD method, another analysis is carried out by using a commercial software, namely HFSS®. From the result, it shows that the FDTD method has a good agreement qualitatively compared to the commercial software with some discrepancy on the S-parameter curve. The disparity of results occurs as the numerator of equation to calculate incident and reflection waves tends to be very small with the increase of frequencies which are being calculated. Moreover, the discrepancy is also evoked by the appearance of higher order modes and the irregularity of EM field inside the rectangular waveguide particularly when it is loaded with anisotropic dielectric material.