Inflection point caustic problems and solutions for high-gaindual-shaped reflectors |
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Authors: | Galindo-Israel V. Veruttipong T. Rengarajan S. Imbriale W. |
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Affiliation: | Jet Propulsion Lab., California Inst. of Technol., Pasadena, CA; |
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Abstract: | The singular nature of the UTD (uniform geometrical theory of diffraction) subreflector scattered field at the vicinity of the main reflector edge (for a high-grain antenna design) is investigated. It is shown that the singularity in the UTD edge-diffracted and slope-diffracted fields is due to the reflection distance parameter approaching infinity in the transition functions. While the GO (geometrical optics) and UTD edge-diffracted fields exhibit singularities of the same order, the edge slope-diffracted field singularity is more significant and is substantial for greater subreflector edge tapers. The diffraction analysis of such a subreflector in the vicinity of the main reflector edge has been carried out efficiently and accurately by a stationary phase evaluation of the φ-integral, whereas the &thetas;-integral is carried out numerically. Computational results from UTD and PO (physical optics) analysis of a 34-m ground station dual-shaped reflector confirm the analytical formulations for both circularly symmetric and offset asymmetric subreflectors. It is concluded that the proposed PO&thetas;GOφ technique can be used to study the spillover or noise temperature characteristics of a high-grain reflector antenna efficiently and accurately |
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