Síntese de fase não uniforme para aberturas circulares e cilíndricas

Abstract

Field synthesis techniques over apertures allow the definition of amplitude and phase distributions over openings that comply with radiation pattern specifications. The goal of this study is to present formulations for the non-uniform phase synthesis of circular and cylindrical apertures. Starting with a formulation that assumes a uniform amplitude distribution, we explore the impact of non-uniform amplitude distributions over apertures with the objective of minimizing the levels of secondary lobes in the radiation patterns. For circular apertures, six amplitude distributions are examined, considering flat-top and Isoflux patterns. For cylindrical apertures, four amplitude distributions are explored, taking into account the cosecant-squared radiation pattern. Once the amplitude and phase distributions are established, the Aperture Method is employed to compute the corresponding radiation patterns. These results are compared with theoretical directivities. Subsequently, the Aperture Method is utilized in this work to validate the proposed amplitude and phase distributions. The utilization of non-uniform amplitude and phase distributions in the design of dual-reflector antennas with circular and cylindrical apertures is also outlined. The reflectors of these antennas are synthesized based on the principles of Geometric Optics. The analysis of the reflectors is conducted using the Method of Moments and the ANSYS HFSS software. As the primary contribution of this work, non-uniform amplitude and phase distributions that meet predefined radiation pattern specifications are emphasized. Furthermore, it was observed that some of the investigated distributions exhibited a reduction in the levels of secondary lobes in the radiation patterns, achieving the initial goal of the work. In parallel with the phase synthesis study, the analytical solution for the Isoflux theoretical directivity was developed in this research.