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Journal of Microwaves, Optoelectronics and Electromagnetic Applications

On-line version ISSN 2179-1074

Abstract

ASSIS, Aline R.; MOREIRA, Fernando J. S.  and  BERGMANN, José R.. GO Synthesis of Offset Dual Reflector Antennas Using Local Axis-Displaced Confocal Quadrics. J. Microw. Optoelectron. Electromagn. Appl. [online]. 2020, vol.19, n.2, pp.177-190.  Epub June 08, 2020. ISSN 2179-1074.  https://doi.org/10.1590/2179-10742020v19i2813.

This work investigates an alternative numerical scheme for the solution of an exact formulation based on Geometrical Optics (GO) principles to synthesize offset dual reflector antennas. The technique is suited to solve a second-order nonlinear partial differential equation of the Monge-Ampère type as a boundary value problem. An iterative algorithm based on Newton's method was developed, using axis-displaced confocal quadrics to locally represent the subreflector surface, thus enabling an analytical description of the partial derivatives within the formulation. Such approach reduces discretization errors, as exact expressions for the mapping function and its derivatives are analytically determined. To check the robustness of the methodology, an offset dual-reflector Gregorian antenna was shaped to provide a Gaussian aperture field distribution with uniform phase within a superelliptical contour. The shaped surfaces were further interpolated by quintic pseudo-splines and analyzed by Physical Optics (PO) with equivalent edge currents to validate the synthesis procedure at 11,725 GHz.

Keywords : Offset dual-reflector antennas; geometrical optics (GO); Monge-Ampère equation; axis-displaced confocal quadrics.

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