Analysis of dispersive characteristics of microstrips on non-diagonal anisotropic substrates using FDTD

We utilize the finite difference time domain (FDTD) method to analyze the dispersive characteristics of arbitrarily-shaped microstrips on fully anisotropic dielectric substrates with a finite thickness. To this end, we extend the existing FDTD algorithms, applicable only to isotropic and uniaxial permittivity tensor, to include non-diagonal permittivity tensors. Assuming a Gaussian excitation pulse, and imposing the interface- and boundary conditions, we first calculate the time-evolution of fields in the simulation domain. Consecutively, by using the Fourier transform, we calculate the frequency dependence of the relevant parameters of microstrips. As examples, we calculate the characteristic impedances, propagation constants, and effective dielectric constants as function of frequency, for different values of the geometrical parameters of the microstrips.