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Tesis:

Contribución al análisis y diseño de reflectarrays impresos de haz conformado en configuraciones complejas.

  • Autor: ARREBOLA BAENA, Manuel

  • Título: Contribución al análisis y diseño de reflectarrays impresos de haz conformado en configuraciones complejas.

  • Fecha: 2008

  • Materia: Sin materia definida

  • Escuela: E.T.S. DE INGENIEROS DE TELECOMUNICACION

  • Departamentos: ELECTROMAGNETISMO Y TEORIA DE CIRCUITOS

  • Acceso electrónico:

  • Director/a 1º: ENCINAR GARCINUÑO, José Antonio

  • Resumen: A contribution to the analysis and design of printed reflectarray antennas is presented in this thesis. The work focuses on the design of reflectarrays in specific configurations, which introduce additional complexity in several facts with respect to the classic approaches used for the design of single offset reflectarrays. The purpose is to improve the electrical performance as well as the accuracy of the analysis and design tools. The thesis is divided into three blocks: the improvement of the reflectarray analysis and pattern synthesis techniques, the validation of the improvements previously introduced through practical designs, and the analysis and design of reflectarrays in complex configurations. It includes multi-feed reflectarrays with multiple beams and dual-reflector configuration with a reflectarray as a subreflector. Some of these examples include the manufacture and measurement of a demonstrator of the reflectarray antenna. The first block deals to the reflectarray analysis and pattern synthesis techniques used in the thesis. The classic reflectarray analysis based on MoM under local periodicity assumption is described, taking into account the incident angle on each reflectarray element. The method is improved to increase the accuracy of the prediction of co- and cross-polar patterns and antenna gain, and to extend the efficiency and applicability of the technique. A phase-only synthesis method based on the Intersection Approach technique is used to synthesize the radiation patterns of reflectarrays. The method can be used in multifrequency pattern synthesis through the inclusion of a constraint limiting the maximum variation in the phase of the reflected field. The algorithm can also include co-polar isolation requirements, which is a common requirement in DBS antennas. In the second block, the analysis and pattern synthesis techniques are demonstrated through two practical reflectarray designs for a Direct Broadcast Satellite (DBS) application. The two designs involve contoured-beam and electrically-large reflectarrays, but with different goals. In the first case, a broadband three-layer reflectarray is designed, achieving a 15% bandwidth in a European coverage. In the second practical design, a 1-metre dual-coverage reflectarray has been designed, manufactured and tested. In this case, the reflectarray generates two independent beams in order to obtain two different footprints in the orthogonal polarisations. The measurements of a breadboard are shown and compared to simulations, and very good agreement is achieved. The third block deals with the analysis and design of reflectarrays in specific configurations: multi-feed reflectarrays with multiple independent beams; and reflectarray subreflector in dual-reflector configurations. Thus, a design procedure for reflectarrays with multiple feeds and multiple shaped-beams is proposed, implemented and validated. For the validation of the methodology, a two-layer printed reflectarray for LMDS central station has been designed, manufactured and measured. The reflectarray has three feed horns that generate three independent shaped beams, covering adjacent areas in azimuth. The reflectarray is illuminated in the Fresnel zone of the feed horns; therefore an enhanced analysis of the reflectarray is achieved through the inclusion of the incident near field coming from the feeds. The analysis of an entire dual-reflector antenna with a reflectarray as a subreflector is dealt with in the second case. This configuration cannot be analyzed with commercial tools and therefore a modular technique based on the Method of Moments and Physical Optics (MoM/PO) is formulated, implemented and validated. In the technique, a simplification is made in PO that allows a significant reduction in the computation time, at the cost of a small phase error in the calculation of the field at the main aperture. However, this phase error does not significantly reduce the accuracy of the technique. The beam-scanning and beam-shaping performances assuming an ideal subreflectarray are studied.