FVTD Characterization of Substrate Effects for Archimedean Spiral Antennas in Planar and Conformal Configurations

This paper describes the application of the Finite-Volume Time-Domain (FVTD) method to characterize the influence of the substrate on Archimedean spiral antennas. The unstructured mesh of the FVTD method permits to model precisely the fine spiral structure and the thin underlying substrate. Time-domain numerical results permit to demonstrate how the substrate affects the distribution of currents propagating on the metallic spiral arms. The substrate influence in the active region of the spiral is described through an effective permittivity which can be related to the transverse mode distribution on the arm of the spiral. Application of the FVTD method to conformal spiral geometries is also suggested in three examples.