Rapid calculation of near-field fluence of HPM antennas

The calculation of accurate fields close to a high gain antenna is important because of personnel hazards and equipment interference possibilities. The authors describe a rapid technique which is suitable for calculation of near-fields of square and circular apertures (or filled arrays); it uses geometric theory of diffraction (GTD) and equivalent edge current integration. The problems with applying GTD to a circular aperture are discussed, and modifications are developed which allow GTD to give satisfactory results for circular apertures. The GTD results are evaluated by comparison with those obtained from double numerical integration. Since the circular aperture is assumed to be symmetric, the near-field patterns are functions of only the polar angle and distance. Both uniform excitation and the important case of tapered excitation have been treated, but only uniform results are given