Study On Integrated Structural-Electromagnetic Optimization Of Cassegrain Antennas

Various structure errors always exist during the process of manufacturing, installation and working of reflector antennas. These errors, including the deformation of the reflector panel, position errors of the feed and sub-reflector and the rotation errors of the sub-reflector, are caused by many factors of the structure such as the dimensions of the structure elements, material properties and environmental loadings, etc. In the design stage, these errors are often uncertain to the designers. These uncertain factors may bring about fluctuations on the electro-magnetic performance of the antennas, and decrease the robustness of a design scheme. It is necessary to quantitatively take these uncertainties into account during the design process. In this paper, the integrated structural-electromagnetic design optimization problem is investigated with quantitative consideration of the various uncertain structure errors for Cassegrain antennas. The main contents are as follows.1. Taking into account the joint effects of various structural errors on the antenna gain, a tolerance optimization approach is proposed for tolerance allocation of various errors. A tolerance optimization model is constructed and a corresponding computing program is developed. The approach was verified by an example.2. An integrated structural-electromagnetic optimization model for Cassegrain antennas under multiple loading cases is constructed. Two loading cases, i.e. the associated elevation angle equals 0° or 90° are considered in this model. The objective is to minimize the gain losses under constrains on the other electromagnetic specifications such as the side-lobe levels and pointing errors etc.. A computing method for solving the optimization problem is given and the corresponding computing program is developed. A numerical example is given and discussed.3. A double-objective robust optimization model for Cassegrain antennas is proposed based on the sensitivity region method. The objective is to minimize the gain loss and the side-lobe level simultaneously. The design variables are the dimensions of the bar elements of the back-up structure. An example of 8m antenna is given with good results.