Fresnel Zone Analysis

The report presents the objectives and results of an investigation of the interference effects of Fresnel region phenomena. Analytical techniques are described that will enable calculation of Fresnel region radiation patterns for monopulse antennas, elliptically or irregularly shaped apertures, and phased arrays. The results from investigations of defocusing techniques, radial E-field in the Fresnel region, effects of reflections in the Fresnel region, antenna to antenna coupling in the Fresnel region, and spurious frequency response are also presented. A unique measurement technique, called Fresnel ring focusing, is described, and gives testimony for a feasible means for obtaining the far-field pattern of a large aperture antenna with measurements taken well within the far-field-Fresnel region boundary. In comparison with other means using the Sommerfield expansion to produce such results, the Fresnel ring focusing technique appears to have many advantages, which are outlined. Recommendations for future investigation including a study of parameter errors and their effect upon the latter technique are included.