Abstract
AbstractThe dome antenna has been proposed for high‐speed scanning of the main beam of the antenna in a wide‐angle range. For the design of the dome antenna, an analysis for the electromagnetic field in the concave side of the conducting sphere is indispensable. In connection with this problem, several studies have been reported on the cylindrical concave surface. However, no report is available to date on the electromagnetic field for a practical concave conducting sphere for which both the source and the observation points are removed from the boundary. This paper describes the results of analysis for this type of electromagnetic problems. First, the integral expressions for the electric field are obtained in the form of a sum of Whispering Gallery (WG) modes and a continuous spectrum. In the derivation of the field expression, spurious diffracted waves are included due to a hypothetical conical absorber, and these waves are eliminated. A scheme is implemented in which the pole contribution of the wavenumbe in the zenith angle θ so that the numerical difficulty is removed. Actual numerical calculations have been performed and the validity and range of applicability have been studied for the expression. It is found that the expression derived in this paper provides a valid field solution for the case where kα (k is the wavenumber and α is the sphere radius) is sufficiently larger than unity and is an integral multiple of π/2.
Published Version
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