The Inclusion of Wall Loss in Electromagnetic Finite-Difference Time-Domain Thin-Slot Algorithms; SAND90-2091 Unlimited Release

Pagination is 3/4 through 40 pages. List of Figures. Illustrations. Formulae. References. Appendix A and B. Printed single sided. Stapled at upper left corner. The authors were with the Radiation and Electromagnetic Analysis Division of Sandia National Laboratories in Albuquerque, New Mexico. We believe that this is the same Douglas Riley who wrote Finite Element Analysis of Antennas and Arrays. Sub-gridding techniques enable finite-difference time-domain (FDTD) electromagnetic codes to model apertures that are much narrower than the spatial resolution of the FDTD mesh. Previous thin-slot methods have assumed that the slot walls are perfectly conducting. As the slot depth-to-width ratio becomes large, interior wall losses for realistic materials can significantly affect the coupling through the slot, and therefore these loss effects should not be neglected. This paper presents two methods for incorporating loss for walls with good, but not perfect conductivity, into the FDTD calculations. The first method modifies an FDTD equation internal to the slot to include a surface-impedance contribution. This method is appropriate for the usual FDTD thin-slot formalisms. The second method includes the losses into a "half-space'' integral equation that can be used by the recent Hybrid Thin-Slot Algorithm. Results based on the two methods are compared for a variety of slot parameters & wall conductivities.…