An asymptotic formula for mode coupling in a finite planar array of circular apertures, which was derived previously, is compared with the exact solution for the case of TE11 mode coupling in two circular waveguides. It is shown that for dominant mode operation of a circular waveguide the asymptotic formula is accurate enough for most practical purposes, even for aperture spacings of the order of a wavelength. © 1980, The Institution of Electrical Engineers. All rights reserved.
Bird, TS & Boomars, JL 1980, 'EVALUATION OF FOCAL FIELDS AND RADIATION CHARACTERISTICS OF A DUAL-OFFSET REFLECTOR ANTENNA.', IEE Proceedings H: Microwaves Optics and Antennas, vol. 127, no. 4, pp. 209-218.
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A receive-mode analysis of a dual-offset reflector antenna consisting of an offset paraboloid and an offset hyperboloid is presented. In this analysis the field scattered from the offset paraboloid is determined using a g. t. d. formulation involving two edge points and a reflection point, if one exists. A method is described for deciding whether there is a reflection point from the gradient of the path length at the edge points. The focal-region fields and the radiation characteristics are computed by numerical integration of the physical optics current on the offset hyperboloid. An experimental antenna operating at 35 GHz is described. Results of measurements of radiation patterns and of the power coupled into a circular waveguide array feed are compared with theory. In each case reasonable agreement is achieved for copolarized directed components. However, the experimental antenna produced higher crosspolarization than expected.