Showing papers by "Per-Simon Kildal published in 1989"
TL;DR: In this paper, the radiation fields of circumferential slots in soft and hard cylinders are calculated for the case in which the slots are excited by a TE/sub 11/circular waveguide mode.
Abstract: The radiation fields of circumferential slots in soft and hard cylinders are calculated for the case in which the slots are excited by a TE/sub 11/ circular waveguide mode. The results are compared to those for a smooth conducting cylinder, showing that the soft surface strongly reduces the intensity of the field radiated along the cylinder whereas the hard surface enhances it. The results are applicable to the design of self-supported feeds for paraboloids, and to the analysis of the line feeds of the radio telescope at the Arecibo observatory. The calculations are confirmed by measurements. >
18 citations
TL;DR: In this article, the authors examined three techniques used for the efficient computation of fields diffracted by a subreflector that has been shaped by geometrical optics synthesis and found that these techniques produce errors in the computed fields that are specific to shaped reflectors.
Abstract: An examination is presented of three techniques used for the efficient computation of fields diffracted by a subreflector that has been shaped by geometrical optics synthesis. It is found that these techniques, which are based on the geometrical theory of diffraction (GTD), produce errors in the computed fields that are specific to shaped reflectors. These errors are examined for a reflector system shaped to produce maximum gain from a tapered feed illumination. The discrepancies are directly related to the caustic being located near an observation point of the GTD calculations. The errors found are localized, and they increase in magnitude as the caustic approaches the main reflector. In a general offset geometry, the location of the caustic may be located arbitrarily close to the main reflector given a prescribed output aperture distribution. For the specific case considered here-the common situation of shaping to produce maximum gain-the caustic is located near the edge of the main reflector and on the reflection shadow boundary. A local correction is derived which creates a uniform solution through the caustic and across the reflection shadow boundary. Away from this point the calculation recedes to the standard GTD solution. >
3 citations