A hybrid differential/mode filtering technique for FDTD analysis of dual-polarization antenna feeds

A new technique for efficient analysis of dual-polarization antenna feeds has been developed. It combines conformal FDTD modelling of the structure, differential decomposition of total fields into incident and reflected, and filtering of the fields through numerical modal templates. The new technique has been validated for matched dual-polarization circular and ridged circular guides, even with coarse discretization producing accurate results. For the practical design of a septum polarizer, excellent agreement with the measurements has been obtained, and a critical parameter which is the 90/spl deg/ phase shift between the polarizations has been simulated with 0.5/spl deg/ accuracy.