Simple Technique for Form-Finding and Tension Determining of Cable-Network Antenna Reflectors

Abstract

T HE development trend of modern space-borne deployable antennas is heading toward larger aperture and higher frequency. Many novel antenna structural patterns for these requirements have been studied and developed [1]. Cable-network antennas, with a self-equilibrium stable tensegrity structural concept, have especially gained wide space applications in recent years due to their good features of low mass, large scale, and compact package volume. Typical examples include several space-qualified projects such as “Thuraya 1-3” geosynchronous satellites, “MBsat” geostationary satellite, and “Inmarsat-4” broadcasting satellite, etc. [2,3]. The reflector surface of this new breed of cable-network antenna is formed by a faceted reflective mesh attached to a network of thin cables, which is called the cable network. As illustrated in Fig. 1, the cable network is composed of two identical paraboloidshaped nets (a front and rear net), which are connected by a series of tension ties (i.e., vertical cables). An outer unfurlable rim structure, namely the so-called supporting ring truss, is coupled to the cable network and has sufficient stiffness and high stability to support the cable network. For concentrating RF radiation, the working surface of this type of cable-network antenna reflector needs to maintain an exact paraboloidal shape, which is directly determined by the mesh configuration of the cable network. Therefore, an appropriate design of mesh configuration is essentially important to achieve a high electromagnetic performance of the antenna reflector. Until recently, there have been several mesh configuration design methods concerning this kind of antenna structure that have been published. Tibert [4] presented a shape-optimal design approach for searching minimal length mesh configurations with three shape-forming steps. Morterolle et al. [5] proposed a new form-finding approach for calculating the geodesic paraboloidal mesh configurations of offset reflectors. Shi et al. [6] proposed a new design methodology to automatically generate pseudogeodesic mesh geometry of spherical and parabolic reflector surfaces. Additionally, Knight et al. [7] studied a new designmethod for creating the geometric configuration of the ring truss of this antenna structure by using line geometry. It is noticeable that the cables in the cable network are a type of flexible structures characterized by strong geometric nonlinearity. They will undergo large displacements and small deformations during the prestressing procedure, which is indispensable in providing the stiffness of the cable-network structure. For acquiring the equilibrium state of mesh configurations and tension distribution of surface cables, a complex nonlinear analysis is normally needed in conventional design methods. To avoid this complex nonlinear calculation, a simple integrated technique is introduced in this study. The main objective of this study is to develop a simple and practical method for the mesh design of cable-network antenna reflectors.