FDTD and FEM Simulation of Microwave Waveguide Polarizers

This paper presents results of comparison of modern effective numerical techniques for the calculation of microwave devices. Nowadays finite difference time domain method and finite elements method are the most frequently used numerical techniques, which are applied for the simulation of electromagnetic fields in various antennas and bounded structures. Modern modifications of these numerical methods and their pro and contras are considered in the paper. Besides, we have compared finite difference time domain technique and finite elements method in the case of calculation of polarization and matching characteristics of microwave waveguide iris polarizers. Using this example we have found that the convergence of the calculated matching characteristics of microwave waveguide devices is fast for both considered numerical techniques. On the other hand, the accuracy of calculation of the phase and polarization characteristics is very sensitive to the number of mesh cells, at which the volume of device structure is divided. It has been found that more than 100 000 tetrahedral mesh cells per structure volume must be used, if calculation of the polarizer’s axial ratio and crosspolar discrimination is performed by finite elements method in the frequency domain with required accuracies of 0.5 dB. If axial ratio and crosspolar discrimination must be calculated with the accuracies of 0.5 dB by the finite difference time domain method, then the utilization of more than 800 000 hexahedral mesh cells per structure volume is required. In has been found that the computation time of the finite elements method in the frequency domain is more than 2 times less than the same time required by finite difference time domain method. Besides, the corresponding number of tetrahedral mesh cells in finite elements method is 10 times less, than the number of hexahedral mesh cells in finite difference time domain method.