SKA超宽带接收机低噪声前端一体化设计研究

The Square Kilometre Array is the world’s largest synthesis radio telescope to be built. One of its advanced instrument program is R&D on the ultra-wideband receivers. One ultra-wideband receiver can replace multiple traditional receivers, to cover a wider frequency range and achieve multi-band observation simultaneously. It has advantages in both engineer implementation and scientific goals study. For wideband receiver, the development of the low-noise front-end including feed and low noise amplifier (LNA) meets challenges. As the device parameters vary with frequency, wideband presents a great challenge to the development of feeds and LNAs. Moreover, the impedance matching between LNA and feed becomes complex. This project propose the integrated design of the low noise front-end of ultra-wide-band receivers, including (1) the integrated impedance matching design for LNA and feed in order to reduce the port return loss; (2) the integrated structure design for the assemble of LNA and feed in order to reduce the ohmic loss of components in front of LNA. In these two ways, the low noise frontend will be achieved, which is helpful for improving the sensitivity of the telescope. This project aims at the Band A receiver of SKA (1.6-5.2 GHz), impedance matching method for ultra-wideband LNA is studied, as well as the integrated design for the front-end of receivers. This work will provide theoretical foundation for the application of ultra-wideband receivers in the SKA second phase.

平方公里阵SKA是即将建设的世界最大综合孔径射电望远镜，其先进仪器项目之一是对超宽带接收机的探索。超宽带接收机可替代多个传统接收机，覆盖更宽的观测频段，实现多频带同时观测，在工程实现和科学目标研究上更具优势。超宽带接收机低噪声的前端研制是难点，包括超宽带馈源和超宽带低噪声放大器LNA。由于射频器件参数随频率变化，超宽带为馈源和LNA各自的设计和优化带来挑战；同时， LNA和馈源的端口阻抗匹配情况也变得更为复杂。本项目提出超宽带接收机前端一体化设计方法：（1）进行LNA和馈源端口阻抗匹配的一体化设计，减少端口的反射损耗；（2）进行LNA和馈源集成的结构一体化设计，减少LNA之前的无源器件欧姆损耗。双管齐下实现低噪声前端，提高望远镜灵敏度。本项目针对SKA波段A（1.6-5.2 GHz）进行超宽带LNA阻抗匹配方法，和接收机前端一体化设计的研究，为超宽带接收机应用在SKA第二阶段奠定理论基础。

本项目基于平方公里阵SKA的先进仪器项目——超宽带单波束接收机展开，超宽带、低噪声的接收机前端研制是难点。主要包括超宽带低噪声放大器LNA和超宽带馈源，具体工作如下：晶体管物理机制分析与选型、电路设计中关键问题、原理图和版图设计、小型化器件焊接、常温和低温性能测试等。重点解决超宽带阻抗匹配问题，研制出1.6-5.2 GHz超宽带LNA，采用两级SiGe HBT晶体管设计，其中一个样机常温时噪声温度测试结果分别为41 K（1.6 GHz）和54 K （5.2 GHz），增益大约为28.46-25.3 dB；制冷到23 K 时，在1.6 GHz和5.2 GHz时噪声温度分别为4 K和5 K，增益大约为32.71-28.74 dB。在四脊型大张角宽带馈源现有技术基础上，设计出一种介质加载超宽带波纹喇叭馈源，仿真结果表明在1-6 GHz范围内反射损耗和方向图均满足要求，实现6：1带宽的超宽带。超宽带接收机可替代多个传统接收机，覆盖更宽的观测频段，实现多频带同时观测，在工程实现和科学目标研究上更具优势。本项目研究为超宽带接收机应用在SKA第二阶段奠定理论基础。