Design And Analysis Of Bidirectional Deployable Parabolic Cylindrical Antenna

Space deployable structures have been widely used in civil engineering and space technology for their ability to transform their configurations to meet the practical requirements (i.e. fold into small volume before launch and deploy into the prescribed configuration when released in orbit). This thesis firstly summarizes the recent development of the deployable structures and their application in space technology, including solar sail, deployable antennas, tape springs etc.A bidirectional deployable parabolic cylindrical reflector for an L-band Synthetic Aperture Radar is presented in this paper, in which a self-deployed antenna with low weight was designed based on the Deployable Support Structure(?). The antenna consists of4curved surfaces formed from thin sheets of composite materials connected by hinges along the edges, and the reflective surface is provided by the front surface. The forming process of the reflector is simulated with ABAQUS/Standard, and the results indicate the ability and potential of this structural concept to satisfy the surface-precision requirement of high frequency antenna.The edge profiles of connecting lines are obtained through geometric analysis, and the cutting pattern of sheets can easily be achieved based on the profile of the parabola. The original concept proposed by Deployable Structure Laboratory at University of Cambridge is extended to obtain the generalized relationship between the geometrical shape of the reflective surface after deployment and the relative rotational angels. It has potential to achieve deployable reflector with continuously transformable aperture and depth of the reflective surface. The phenomenon of rotational limit observed both in finite element analysis and real paper model is explained mathematically.The fold and deployment process are validated through a scaled model. The reflector is driven to the prescribed configuration, using the self-stored strain energy in sheets and tape springs which are attached to the sheets, and after deployment the structure can be locked by the hinge. A scaled model, including design and manufacture, was demonstrated to validate the process from the folded state to the fully deployed state.The non-contact synchronous vision measuring method was used-instead of the traditional acceleration transducer because of the significant effect of its weight on the vibration of the light-weight and flexible structures-to test the basic frequency of the scaled model, and the test results gave the verification of the finite element analyses. The material properties of the PP sheets are obtained through series of uniaxial tensile tests.Static, modal, harmonic response, and transient response analyses of the full-sized reflector structure were modeled with the commercial FE package ABAQUS. Several stiffness improving methods are designed to increase the fundamental natural frequency, and the results indicate that adding side walls and large curved tape springs are the two reasonable methods to optimize the reflector. The modeling techniques were developed to predict the structural dynamic behavior of the reflector and the results show that the first natural frequency was0.865Hz, and the frequency response analyses predict strong peaks at0.86Hz,1.71Hz and3.0Hz, which are the first three natural frequencies of the reflector.The preliminary analyses of radiation patterns of the reflector after deployment were conducted with commercial electromagnetic software Feko, and the linear feed array consists of horn antennas was used to feed the parabolic antenna.Compared with the existing unidirectional deployable antenna, this bidirectional deployable antenna can be applied to larger-size antennas and has better performance because the glass-woven tape connections were substituted with more reliable traditional hinges. This proposed structure has very high stiffness-to-mass ratio because of its hollow solid construction.