Design And Analysis Of A Planar Thin Film Reflectarry Antenna

With the development of space science and technology, space structure is getting larger. To save launch cost, deployable structure is becoming more and more widespread. Planar membrane reflectarray antenna that can be folded is presented in this article. And analysis, production as well as testing of small-scale model with effective reflective area of 2mx2m are also accomplished.Abundant domestic and foreign literatures are looked up then on this basis application and research status of space deployable structure at home and abroad are summarized in this article. These application examples provide a lot of valuable design method and experience for our antenna design.Planar membrane reflectarray antenna combines the merits of curved surface reflector antenna and phased array antenna. It is a novel antenna which replaces the parabolic reflector with thin plane or conformal array reflector. Planar reflector is easier to implement and maintain in contrast with parabolic reflector. Based on the JPL’s conceptual design of two dimensional deployable reflectarray antenna the design scheme is modified. The boundary of tensioning membrane surface is round instead of parabolic curve and the driver of horizontal deployment unit is power system combined torsional spring with steel tape hinge. The inflatable tube is still circular aluminum laminate boom strengthened by steel tape. At last the laboratory model of the design scheme is achieved.In this article, it has been proved theoretically that the optimal boundary should be circle to make planar space membrane structure to be equal tensile force extension. Nonlinear form-finding finite element method of cable membrane structure has also proved this point indirectly. A new tension method of membrane with inner and outer cable is proposed. The specific calculation of all cable tensions on this condition is also given in the article. The research examines the influence of boundary span number on structure’s axial pressure and concludes that odd span numbers will produce relatively small axial pressure for support structure. In new tension method of membrane, required cross sectional area and weight of cable are both smaller than traditional tension method. Moreover, with this tension method membrane surface wrinkle will be less if supporting structure deforms.The mechanical properties of steel tape in two bending cases, folded bending and rolled bending, are studied respectively in this article. The unfolding moment formula in two bending modes is deduced through the theory of thin shell and is verified by the finite element method. The mechanical properties of steel tape hinge are analyzed to conclude that its unfolding moment is independent with the interval of steel tape. The ability resistant to flexion in plane and torsion is poor. And there is reverse buckling after steel tape hinge is deployed from 90° folded status. So the steel tape hinge must be used with spring hinge. The laboratory method to measure buckling moment and unfolding moment of steel tape hinge is presented.It is one difficulty of whole antenna system to analyze and control the deployment process of inflatable tube. On the basis of an overall analysis of nonlinear hinge model, rolled model of inflatable tube as well as axial coupling of air and inflatable tube, a kind of rolled hinge model considering axial coupling of air and inflatable tube is proposed. And the influences of three factors, air pressure of inflation, steel tapes on the inner tube wall and Velcro on the outer tube wall, on the deployment process of inflatable tube are considered.It is one difficulty of whole antenna system to analyze and control the deployment process of inflatable tube. On the basis of an overall analysis of nonlinear hinge model and rolled model of inflatable tube as well as the impact of aerodynamics on inflation pressure, a kind of rolled hinge model considering the influences of inflation pressure, steel tape of inner tube wall and nylon link of outer tube wall on the deployment process of inflatable tube is proposed. The dynamic equation of multi-body system is established by Newton-Euler method to analyze the deployment process of whole system. The visualization of simulation and analysis is also realized with OpenGL.According to relevant specifications of planar reflectarray antenna, a two dimensional deployable planar reflectarray antenna with effective reflective area of 2m×2m is produced. Some suggestions of manufacture craft in actual production are also put forward. Test framework for the antenna deployment is fabricated. And the deployment of two dimensional deployable planar reflectarray antenna is tested by both horizontal slide and vertical suspension method. The surface precision of reflectarray antenna after deployment is an important index of antenna. The video measurement system is built based on PhotoModeler in this article and the surface precision of small-scale model of reflectarray antenna is measured. The result shows that the surface precision can satisfy the index. The test result is compared with the analysis of simulation software and the major reason of error is described.