射电天文X波段极化网络一体化设计与研究

射电天文望远镜中极化网络一般由极化器、波导同轴转换器、耦合器等几部分组成,为了获取最高限度的系统灵敏度,极化网络在射电天文低温接收机中会置于低温真空杜瓦20 K 温区,使其对接收机噪声温度的贡献降到最低。通过对极化网络的深入研究设计了一种基于隔板结构的X 波段极化器、耦合器和波导同轴转换器一体化结构。该设计既实现了极化器的线圆转换功能又实现了-30 dB 噪声耦合。测试结果表明该设计拥有良好的轴比、耦合度和驻波特性。同时一体化设计进一步减小了无源器件之间的级联,使低温低噪声放大器之前的馈源网络插入损耗进一步降低,提升了射电望远镜的接收灵敏度。

Research on Radio Astronomy X-Band Polarization Network Integrated Design

A polarization network on radio telescopes generally consists of a polarizer, a waveguide-to-coax adaptor, and a directional coupler etc. Usually, in order to obtain the maximum system sensitivity, the polarization network will be worked at 20 K platform in the cryostat of cryogenic receivers,which decreases the receiver noise temperature to lowest.Through in-depth study of the polarization network, this paper designs an X-band polarizer,coupler and waveguide-to-coaxadaptor integrated structure based on a septum structure. This design not only realizes the conversion of circularly polarized wave to linearly polarized wave, but also obtains the noise coupling of -30 dB. The measured results show that the design has good axial ratio, coupling and VSWR characteristics. Meanwhile, the integrated design further reduces the cascading between passive devices to get the lowest insertion loss of the feed network in front of the cryogenic low noise amplifier,which enhances the receiving sensitivity of the radio telescope.