面向FAST的宽带高灵敏度相控阵馈源系统设计关键技术研究

The new generation of receiver system for radio telescope is developing towards a high comprehensive performance of broader working bandwidth, higher sensitivity and larger field of view as well as faster survey speed. The phased array feed (PAF) with both broadband and high sensitivity will be the development trend of high performance feed for radio astronomy in the future. It is hopeful to correct the Coma effect caused by the deformation and direction errors of the reflector, improve the antenna efficiency, eliminate radio frequency interference and suppress standing wave caused by near-field scattering of the feed cabin so as to speed up continuous scanning and survey of large sky area for large radio telescopes.. The design scheme of broadband (700 MHz-1.5 GHz) high-sensitivity phased array feed system for FAST will be studied in this project. We will focus on key technologies in the hardware design of wide-band PAF low-noise array, the synthesis algorithm of digital beam synthesis pattern in complex environment and the performance evaluation of PAF system. The system simulation analysis and experimental verification of the first broadband low-noise PAF system prototype at room temperature will be carried out. The proposed research will set up solid foundation both theoretically and experimentally for future development of the FAST L-band broadband phased array feed system.

新一代射电望远镜接收系统向着集更宽的工作带宽、更高的灵敏度、更大的观测视场和更快的巡天速度于一体的高综合性能方向发展。兼具宽带和高灵敏度的相控阵馈源（Phased Array Feed,PAF）作为射电天文高性能馈源的发展趋势，有望纠正反射面的形变和指向带来的相差，提高天线效率，抑制射频干扰，消除馈源支撑近场散射引起的驻波，有利于大型射电望远镜的大天区连续扫描与快速巡天观测。.本课题以大型射电望远镜FAST为依托，首次开展面向FAST的宽带（700MHz-1.5GHz）高灵敏度相控阵馈源的系统设计方案的研究，解决宽带PAF低噪声阵列硬件设计、复杂环境下数字波束合成方向图综合算法以及PAF系统性能评估方面的关键问题和技术瓶颈。完成第一代常温宽带低噪声PAF系统原理样机的系统仿真分析和观测实验验证。为未来FAST L波段宽带高灵敏度相控阵馈源系统的全面研制奠定坚实的理论和实验基础。

本项目结合射电望远镜光路分析，提出有源接收集成一体化的密集型PAF系统设计方案，开展人工智能优化算法的PAF波束赋形研究，完成 FAST P-L波段有源PAF系统设计样机加工及实验平台搭建，实测相控阵馈源系统噪声温度小于50K，编写了基于模拟波束合成和数字波束合成的大规模相控阵馈源混合算法程序。项目发表SCI/EI论文12 篇(第一作者、通讯作者论文7篇)，受理专利1项，授权软件著作权1部。本项目相关PAF系统设计研究成果用于上海天文台、中国电子科技集团公司“C波段制冷相控阵馈源的研制”项目，设计的宽带低噪声馈源接收系统用于贵州师范大学4.5米天线阵列，已成功观测到脉冲星与中性氢，设计的馈源形式用于CMB毫米波90-150GHZ硅堆叠天线与阵列;本项目研究成果《大规模相控阵馈源混合波束合成算法软件》，已用于子午工程II期行星际闪烁射电望远镜大规模相控阵馈源波束合成实验测试和调试验证。