THEORETICAL AND EXPERIMENTAL STUDY OF THE SCATTERING BEHAVIOR OF A CIRCUMFERENTIALLY -LOADED SPHERE.
MICHIGAN UNIV ANN ARBOR RADIATION LAB
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The electromagnetic scattering behavior of a metallic sphere loaded with a circumferential slot in a plane perpendicular to the direction of incidence is investigated. The slot is assumed of small but finite width with a constant electric field across it, and under this assumption, the analysis of external fields is exact. The scattered field is obtained by superposition of the field diffracted by an unloaded sphere and that radiated from the excited slot, with the radiation strength and phase determined by the loading parameters. Thus the scattering behavior is determined by the loading admittance and the position of this slot. The numerical study is restricted to the frequency range corresponding to 0 ka 10.0, and the results presented are primarily for passive loading. The maximum and minimum back scattering cross sections and the loading needed to attain these are presented for different loading positions. The bistatic scattering patterns are computed for a sphere loaded for zero back scattering and from these the back scattering null widths are obtained. The extreme total scattering cross sections are evaluated using the forward scattering theorem and, for small values of ka, the result is compared with that obtained by direct integration of the differential cross sections. Experimental data, obtained using a metallic sphere with an equatorial slot backed by a radial cavity of adjustable depth, is presented for the surface field and back scattering measurements. The results are compared with the computed data. Author
- Radiofrequency Wave Propagation