The Finite-Difference Time Domain Method for Solving Maxwell's Equations

This chapter gives update equations for electric and magnetic fields used in the 3D-finite-difference time domain (FDTD) computation and those in the 2D cylindrical coordinate system. The FDTD method uses the central difference approximation to Maxwell's curl equations, which are Faraday's law and Ampere's law, in the time domain. The chapter then describes subgridding technique, which allows one to employ locally finer grids. Next, it explains an absorbing boundary condition, which is needed for the analysis of electromagnetic fields in an unbounded space. There are two types of absorbing boundary conditions, namely differential-based absorbing boundary condition and material-based absorbing boundary condition. Representations of lumped sources and lumped circuit elements such as a resistor, an inductor, and a capacitor are described. Also, representations of a thin-wire conductor and the lightning return-stroke channel are discussed. Finally, representation of a nonlinear element such as a surge arrester is explained.