Design optimization studies for large-scale contoured beam deployable satellite antennas

摘要

Satellite communications systems over the past two decades have become more sophisticated and evolved new applications that require much higher flux densities. These new requirements to provide high data rate services to very small user terminals have in turn led to the need for large aperture space antenna systems with higher gain. Conventional parabolic reflectors constructed of metal have become, over time, too massive to support these new missions in a cost effective manner and also have posed problems of fitting within the constrained volume of launch vehicles. Designers of new space antenna systems have thus begun to explore new design options. These design options for advanced space communications networks include such alternatives as inflatable antennas using polyimide materials, antennas constructed of piezo-electric materials, phased array antenna systems (especially in the EHF bands) and deployable antenna systems constructed of wire mesh or cabling systems. This article updates studies being conducted in Japan of such deployable space antenna systems [H. Tanaka, M.C. Natori, Shape control of space antennas consisting of cable networks, Acta Astronautica 55 (2004) 519-527]. In particular, this study shows how the design of such large-scale deployable antenna systems can be optimized based on various factors including the frequency bands to be employed with such innovative reflector design. In particular, this study investigates how contoured beam space antennas can be effective by constructed out of so-called cable networks or mesh-like reflectors. This design can be accomplished via "plane wave synthesis" and by the "force density method" and then to iterate the design to achieve the optimum solution. We have concluded that the best design is achieved by plane wave synthesis. Further, we demonstrate that the nodes on the reflector are best determined by a pseudo-inverse calculation of the matrix that can be interpolated so as to achieve the minimum deviation from the reflectors' ideal shape. The RMS characteristics of the "cable network" in any deployable space antenna are constrained from exactly achieving the ideal contour because they ultimately contain very small plane facets. The effect of these plane facets on the characteristics of the contoured beams can be identified, however, by numerical simulations. Then these characteristics can be improved with the node locations being optimized as these simulations are undertaken. This process, however, must take into account a non-dimensional parameter. This parameter is based on the frequencies being employed, the plane facet size, and the angle of plane wave from the z-axis. When this optimization process is undertaken, the optimum location of the nodes in the "cable network" that compose the space antenna reflector can be precisely identified.