Study On Integrated Structural-terminal-Electromagnetic Optimizetion Of Cassegrain Antennas

Various structure errors of a reflector antenna have great effects on its radiation properties,and must be taken into account quantitatively in design stage.Structure errors include manufacturing and assembly errors as well as structural deformations due to various loads.In addition to self-weight,environmental thermal load is one of the most important loads which cause the structural deformations.In this thesis,the problem of integrated structural-thermal-electromagnetic simulation and design optimization for reflector antennas,in particular for Cassegrain antennas,is investigated.The main contents are as follows:1.Based on the ASHRAE clear-sky model and using the radiation parameters of Beijing region,the temperature field analysis of the main reflector of a Cassegrain antenna with 8m diameter is implemented.The considered factors which cause the heat flow over the reflector surface include the solar radiation,convection and environmental longwave radiation.The phenomenon called “solar cooker” appeared on the sub-reflector is also analyzed and discussed.2.An approach of integrated structural-thermal-electromagnetic simulation for Cassegrain antennas is proposed with consideration of both self-weight and temperature loads.As a typical example,the electromagnetic properties of an 8m antenna is analyzed under several sets of environmental temperature,solar incident angle and antenna elevation angle.The effect of the number of rings partitioned of the main reflector on the side-lobe level is discussed through numerical simulation.3.Two optimization models,namely the integrated thermal-structural optimization model and the integrated structural-thermal-electromagnetic optimization model are proposed respectively by applying the idea of robust design.In both models,the cross sectional areas of the members of the backup structure are taken as design variables and the elevation angle is considered as an uncertain parameter.To solve the optimization problems effectively,a surrogate model-based optimization method is proposed.The reasonability of the model and the effectiveness of the method are verified by an example.