FAST 宽带双极化多波束馈源设计

摘要

双极化和宽带设计可以提高射电天文望远镜的观察效率;多波束技术可以拓宽视场,提高观察速度.利用多个独立的馈源偏焦放置实现的多波束反射面天线,具有结构简单、随频率变化性能稳定等优点.设计了一个针对500 m口径球面望远镜(five‐hundred‐meter aperture spherical telescope ,FAST )的双极化、宽带19波束馈源,给出了馈源的实现方式和测试结果,利用馈源的幅度和相位辐射方向图,计算了由主动球面形成的多波束瞬时抛物反射面天线的性能.分析了剩余球面由于能量泄露对瞬时抛物反射面产生的影响.该系统级的设计方法及设计结果可为FAST 将来的频段更换等升级改造提供设计参考和数据参考.%In radio telescope ,the dual‐polarization and broadband design is used to improve surveying efficiency , and the multi‐beam technique is usually employed to widen the field of view and to increase the surveying speed . M ultiple independent off‐focal feeds can form a multi‐beam reflector antenna .The multi‐feed‐per‐beam reflector antenna has a simple structure but stable performance w ithin w ide bandw idth .A dual‐polarization and broad‐band 19‐beam feed for the five‐hundred‐meter aperture spherical telescope (FAS T ) is designed .Design method , designed and measured results are presented .Based on the primary amplitude and phase radiation patterns of the feed ,the performance of the multi‐beam instantaneous parabolic reflector antenna deformed from an active spherical main reflector in real time is calculated ,and the influence of the remaining spherical surface on the illu‐minated parabolic surface due to leakage energy is analyzed .This system‐level design method and design results provide design references and data references for the FAS T reformation such as frequency‐band replacement in the future .