Analysis of the Resonant Cavities Using the FDTD Scheme with Effective Permittivities Formulae

An efficient expression of the effective permittivities along x-, y-, z-direction is obtained by analogy with the circuit concept of series-parallel connection of capacitance. Under the condition of numerical stability, the approximate formulae of effective permittivities for various inhomogeneous cell mesh are combined with the Finite Difference Time Domain (FDTD) scheme of arbitrary spatial cell size to calculate resonant frequency of 3-D cavity. The results are in agreement with that of conventional FDTD method, but the proposed method can save computing time and memory.