A Method To Achieve S-parameters Of Waveguide From FDTD Simulation And Its Applications

Finite-Difference Time-Domain Method (FDTD) is a widely used numerical method for electromagnetic simulation. In the past three decades, there are more and more applications of that method. Now the method can be applied to antenna design, microwave circuit simulation electromagnetic scattering, and so on. When applying FDTD to analyze a practical problem, the programming is so complicated that it is difficult to perform. Thus, many software companies have developed some electromagnetic simulation software. With those software, it is easy to build the geometric model and assign simulation parameters.This paper combines the basic theory of electromagnetic and an electromagnetic simulation software based on Finite-Difference Time-Domain (FDTD) method. The software only provides S-parameters at the feed points, not on the cross sections. This cannot satisfy the practical requirements. A method of computing Poynting vector from the steady-state data saved by the software to obtain S-parameters is presented in this paper. Meanwhile, numerical errors are analyzed with different simulation conditions such as time steps, grid sizes, loads and absorbing boundary conditions. It shows that the method is valid and practical. Waveguide partially filled with water is computed as an example by this method. Moreover, the method can be applied to calculating S-parameters of other systems. This paper also simulated a attenuator and a three pins tuner. The three pins tuner was used for Yangshao-1 microwave chemical experiment system.In one word, the method based on Poynting and FDTD is valid for calculating the S-parameters. The results of BJ-22 are similar to FEM's. What will be done is to prove the validity of the waterload's results and improve BJ-9 experiment system.