RADIATION AND SCATTERING OF A SQUARE ARCHIMEDEAN SPIRAL ANTENNA USINGFDTD

A Finite-Difference, Time-Domain (FDTD) analysis of a square Archimede an spiral antenna is performed to calculate antenna gain and scatterin g patterns. The spiral is mounted in a large, conducting ground plane and is backed by an air-filled or absorber-filled cavity. The effects of resistive sheets placed over the spiral are also evaluated for both radiation and scattering. Total-field FDTD calculations are used to c ompute the gain patterns, while a specially-modified scattered-field a pproach for aperture antennas in infinite ground planes is used for th e scattering results. Comparisons are made with calculations done with a Finite Element method and excellent results are obtained.