Research Of The Multi-conductor Transmission Lines With The Finite Difference-Time Domain Method

Supported by National Natural Science Foundation of China under grant No. 50077006, the finite difference time-domain (FDTD) method is researched to solve the model of multi-conductor transmission lines (MTLs) in this paper. The main contributions are as follows:1. Based on Maxwell's equations, with the complex depth method the ground return impedance of the multi-layer soil is obtained under given conditions. At the same time, the vector fitting method and the inversion Laplace transform are adopted to simplify the time-domain convolution.2. For the nonuniform MTLs, the exponential approximation model based on the stationary wave transform is put forward, which avoids the impedance discontinuity and can be used for the lossy nonuniform MTLs.3. The iterative formulas of the FDTD method to solve the uniform MTLs model without frequency-dependent parameters are given and extended to solve more complicated model when the incident wave is uniform plane wave.At last, the method proposed is demonstrated to be true and effective through many examples in this paper.