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The surface-accuracy design criterion for the next-generation reflector antennas for the deep-space instrumentation project in China was 0.1 mm rms. However, these antennas have no radome or air-conditioned ventilation to protect against solar radiation. Therefore, the effect on the antenna's electromagnetic performance of thermal deformation due to solar radiation must be carefully evaluated. For this engineering problem, a 40-m reflector antenna was selected as the research object. First, the heat fluxes from direct solar radiation, sky-scattering radiation, and ground-reflected radiation on the antenna's surface were calculated, based on the antenna's location, date, and time. Second, the temperature distribution of the whole antenna was obtained with the Finite-Element Method (FEM), considering three methods of heat transfer: conduction, convection, and radiation. A temperature experiment was then designed via a 7.3-m Cassegrain antenna. The results indicated the validity of the previous heat flux and temperature analyses. Engineering knowledge of the thermal impact on the antenna's radiation was essential to improve the overall design and construction of the antenna. Third, a thermal-structural analysis was carried out with ANSYS. Finally, the electromagnetic parameters of the antenna were calculated using a far-field pattern formula, and three main electromagnetic parameters - the gain loss, the sidelobe level, and the pointing error - were considered in detail. The results of the analysis showed that the degradation of the electromagnetic performance was not only dependent on the rms amount of structural deformation, but also on the distribution of the deformation, especially for the sidelobe level and pointing error. The analysis method and results can be referenced for the design of next-generation reflector antennas.
Date of Publication: Oct. 2012