FDTD modeling of magnetized ferrites using Z transforms

Ferrite materials have numerous applications in microwave systems, especially in the implementation of non-reciprocal devices like isolators, circulators and phase shifters. The anisotropic and dispersive nature of ferrites makes it very difficult to obtain exact analytical solutions to electromagnetic problems where a ferrite is present. The finite-difference time-domain (FDTD) method is one of several numerical methods that has been developed to treat complex electromagnetic problems. A simple formulation of a model for ferrites, based on the Z transform method is presented. The method is easy to implement, extensible to more complex models and it does not require complex changes in existing FDTD code. Comparison between the simulation and experimental data from an YIG microstrip resonator shows good agreement.