Study On Coupled Structural-electromagnetic Modeling Of Offset Parabolic Reflector Antennas

The offset reflector antennas now form a large class of antennas used inlow-Earth-orbiting mobile communication satellites, search or surveillance radars, etc.With the development of offset reflector antennas with high performance, growingdemands for high frequency, low sidelobe level and reduced mass have broughtstructural design and manufacturing process stringent requirements. Furthermore, theexisting design approaches dealing with the electric performance and structure ofantennas separately propose more challenges to structural design and manufacture.Therefore, it is necessary to study the coupled structural-electromagnetic problem ofoffset reflector antennas so as to find out the prime structural factors which have a greateffect on electromagnetic performances, thereby reducing the requirements of minorstructural factors effectively. The application of this model could offer antennadesigners a theoretical guide for reasonable structural design.First, the coupled structural-electromagnetic model of the offset reflector antenna isdiscussed and developed. The structural factors affecting the performance of the offsetreflector antennas mainly consist of the reflector surface errors and the feed errors.Particularly, the reflector surface errors mainly come from two factors. One is thesystematic error of surface distortion due to the exterior loads acting on the antennasuch as solar radiation, vibration, and wind etc; the other is the random error broughtabout by the manufacturing process and assembly. Meanwhile, the feed errors includethe position displacements and pointing deviation which could degrade the antennaperformance obviously. Considering the structural elements mentioned above, thecoupled structural-electromagnetic model of the offset reflector antenna is discussed andverified by using the aperture field method.Second, based on the coupled structural-electromagnetic model proposed, aspaceborne offset parabolic reflector antenna on Ku band is discussed. The influence ofthermal distortions caused by solar radiation on the electromagnetic performances of theantenna under several conditions are analyzed and compared. The results indicate that itis necessary to conduct the coupled structural-electromagnetic analysis.Finally, the coupled structural-electromagnetic software platform of offset parabolicreflector antenna is designed. The spaceborne offset parabolic reflector antenna on Kuband is studied as an example to verify this software platform. And the analysis resultsare compared with that of the EM software FEKO and Ruze’s Equation. The compared results show that the software platform designed is accurate and effective.