宽带相控阵馈源技术研究

Phased array is a type of antenna which can change the radiation pattern by controlling the feeding phase of array element. By controlling the phase, the antenna pattern of maximum points can be changed and beam scanning can be realized. Phased array can work as the feed of reflector antenna. Through digital beam synthesis networks and introducing amplitude and phase-weighting to the signal received by the array antenna, several instantaneous beam and beam-scanning can be formed. This method is called the phased array feed (PAF) technology. . In radio astronomy applications, PAF provides the possibility of observation with a number of closely overlapped beams, which greatly extends the Field-of-View（FoV）of the radio frequency interference(RFI) from human activities and reflector deformation due to gravity and other factors. Thus it is called one of the key technologies for the next generation of radio telescopes. . The project aims on independent research and development of broadband phased array feed for giant telescope FAST L-band receiver. By using miniaturized broadband antennas, new feed network, Photonic band-gap new electromagnetic materials and the genetic algorithm, this project focuses on PAF broadband element and array design, as well as precise digital beam forming algorithms research. This project will provide certain technical support to the design of phased array feed for domestic radio telescope.

相控阵天线是通过控制天线阵列中的辐射单元的馈电相位来改变方向图形状的天线。通过控制相位，可以改变天线方向图最大值的指向以达到波束扫描的目的。将相控阵作为反射面天线的馈源，通过数字波束合成网络，对阵列天线接收到的信号进行幅相加权并合成，形成数个瞬时波束进行波束扫描的方法，称为相控阵馈源（PAF）技术。. 在射电天文领域，相控阵馈源可用于产生多个紧密交叠的波束，有效扩大射电望远镜视场，提高巡天效率，还可以消除人为因素对射电望远镜的电磁干扰以及重力引起的反射面形变，被称为下一代射电望远镜的关键技术之一。. 本项目以巨型望远镜FAST为依托开展L波段宽带相控阵馈源的自主研发，拟在采用小型化宽带天线、新型馈电网络、光子带隙新型电磁材料以及遗传算法等的基础上重点研究宽带PAF阵元设计、组阵技术及数字波束成形精确算法。旨在为国内射电望远镜相控阵馈源的设计提供一定的技术支撑。

相控阵馈源技术（PAF）作为一种新型馈源是将相控阵天线作为反射面天线的馈源，通过数字波束合成网络，对阵列天线接收到的信号进行幅相加权并合成，形成多个瞬时波束或进行波束扫描。其具有传统多波束馈源所不具备的优点：可以形成紧密交叠的波束，实现连续的天空覆盖，从而更为有效地扩大射电望远镜的视场，提高巡天速度。通过适当的激励，可以补偿馈源偏焦造成的相位误差，将偏轴波束的增益提高至与轴向波束相当的水平，此外，还可以通过控制副瓣电平降低接收噪声以及在期望方向形成零陷消除RF的干扰等问题。本课题以500米球面射电望远镜（FAST）19 波束指标为参照，完成了低噪声宽带相控阵天线阵列的设计、波束合成因子的计算以及相控阵馈源系统的评估，给出了3种阵列单元的备选方案，并完成了小型阵列1*4单元组阵和中型阵列4*6阵列的仿真工作，以及单元零件的加工，相关的测试工作正在进行。该课题研制的4-8GHz的宽带相控阵馈源单元和阵列将作为SKA Pathfinder PHAROS2的备选方案，将其等比缩放至L波段，可为FAST和新疆110米的相控阵馈源提供相控阵馈源的方案支持，此外，该项目研究的宽带相控阵馈源的设计方法、波束合成因子的计算和系统评估的内容将为射电天文相控阵馈源技术的发展提供一定的理论和技术支撑。