Collaborative Research: Development of a Millimeter-wave Phased Focal Plane Array

目前，一个典型的大型毫米波射电望远镜的成本超过1亿美元，但最先进的焦平面外差接收器阵列覆盖不到10%的有用视场，敏感区域之间有很大的间隙。此外，单个组件无法有效地与天线集中的能量耦合，从而使望远镜在天空中的分辨率降低了20%，并且通常会丢失约一半的可用信号。合作者N.埃里克森和B。分别由马萨诸塞州大学和杨百翰大学的Jeffs博士提出的是利用相控阵馈电技术构造焦平面阵列。这种方法与传统的馈电喇叭不同，它使用一组小天线馈电来合成主天线的单个馈电。这样的阵列收集焦平面中的所有能量。该焦平面阵列的元件的相组合允许合成最佳尺寸和幅度/相位分布的喇叭，以提高望远镜分辨率并补偿望远镜表面误差。虽然相控焦平面阵列在射电天文学领域有着巨大的革命性前景，但大型二维阵列的成功部署仍然需要几年时间，因为它需要克服制造、加工和包装方面的障碍。 Erickson博士和Jeffs博士计划测试生产具有非常小的元件间距的接收器前端的概念，演示现代数字信号处理器进行波束矢量组合的实用性，并开发用于组合波束、校准阵列和处理最终数据流的计算算法。 这个为期3年的项目的目标是一个8 × 8阵列，覆盖70 - 95 GHz的频率范围，100 MHz带宽，低温冷却，安装在国家射电天文台的100米绿色银行望远镜上。除了为未来大型，高效，二维毫米波接收器阵列铺平道路外，埃里克森/杰夫斯项目将涉及两个合作机构的工程和天文学研究生，并为五所大学天文学本科生实习计划中有才华的本科生提供高级研究课题。 因此，它将教育成员的新一代研究人员在复杂的艺术毫米波阵列仪器。 这项工作的资金由NSF的天文科学部通过其先进技术和仪器计划提供。

Presently, a typical large mm-wave radio telescope costs more than $100M but state-of-the-art arrays of focal-plane heterodyne receivers cover less than 10% of the useful field of view with large gaps between sensitive areas. Moreover, individual components are not efficiently coupled to the energy concentrated by the antenna, reducing the telescope's resolution on the sky by 20% and typically losing about half of the available signal. The key new development proposed by collaborators Drs. N. Erickson and B. Jeffs of the University of Massachusetts and Brigham Young University, respectively, is the construction of focal-plane arrays utilizing phased array feed techniques. This approach differs from traditional feed horns by using a cluster of small antenna feeds to synthesize a single feed for the main antenna. Such an array collects all of the energy in the focal plane. Phased combination of the elements of this focal plane array allows one to synthesize horns of optimal size and amplitude/phase distribution to enhance the telescope resolution and compensate for telescope surface errors. At the same time they produce nearly as many beams on the sky as elements in the array.While phased focal-plane arrays hold great promise for revolutionizing the field of radio astronomy, successful deployment of large two-dimensional arrays is still several years off, for it requires hurdles to be overcome in manufacturing, processing, as well as packaging. Drs. Erickson and Jeffs plan to test concepts for producing receiver front-ends with very small element spacings, demonstrate the utility of modern digital signal processors to do the vector combination of beams, and develop computational algorithms for combining the beams, calibrating the array, and processing the final data stream. The goal of this 3-yr project is an 8 x 8 array covering the frequency range 70 - 95 GHz with 100 MHz bandwidth, cryogenically cooled and installed on the 100-m Green Bank Telescope of the National Radio Astronomy Observatory.In addition to paving the way for future large, efficient, two-dimensional mm-wave receiver arrays, the Erickson/Jeffs project will involve engineering and astronomy graduate students at the two collaborative institutions and provide advanced research topics for talented undergraduate students in the Five College Astronomy Undergraduates Internship Program. It will thereby educate members of a new generation of researcher in the complex art of mm-wave array instrumentation. Funding for this work is being provided by NSF's Division of Astronomical Sciences through its Advanced Technologies and Instrumentation program.