In recently decade years, finite difference time domain method (FDTD) is the most popular numerical method in the electromagnetic fields, such as the microwave circuit, antennas, and etc [1-2]. In order to deal with inhomogeneous dielectric in the interface, the usually method is to plot out the mesh along the interface in two kinds of dielectric [3], but this will limit the size of unit grid which is much smaller, and it increases computation time. In this paper, by using analogy with the circuit concept of series-parallel connection of capacitance, the approximate formulae of effective permittivities for various inhomogeneous unit grid are deduced. Under the condition of numerical stability, these formulae are combined with FDTD method of arbitrary spatial mesh to calculate frequency of the resonant cavity. This proposed method can save computing time and memory than the conventional FDTD method. These effective permittivities formulae will be applied in other difference methods for electromagnetic problem.
展开▼
