一种宽带四脊波导正交模极化耦合器

坐落于贵州天然喀斯特地形的500 米口径球面射电望远镜(FAST),其低噪声接收机系统需要高性能正交模极化耦合器,对此,提出了一种四脊波导形式宽带正交模极化耦合器快速有效的设计方法:首先分别设计四脊波导正交模极化耦合器的两个关键部分,然后进行整体优化,为了改善带内阻抗匹配性能可以在同轴输出端口的内探针引入阶梯匹配环。使用这种方法研制的FAST L 波段极化器工作带宽达到2 颐1,在整个带宽范围内极化器的反射系数小于-20 dB,极化耦合水平低于-43 dB,带内插入损耗优于0. 15 dB,仿真和实测结果有很好的一致性。提出的设计方法适用于各种频率范围的宽带四脊波导正交模极化耦合器的设计。

A Broadband Quadruple-ridge Orthomode Transducer

The five-hundred-meter aperture spherical radio telescope (FAST) is the largest radio telescope in the world, which is located in the natural karst terrain of Guizhou province. The low noise receiver system of FAST requires high performance orthomode transducer (OMT), so, this paper proposes a quick and efficient design method of broadband quadruple-ridge waveguide orthomode transducer (OMT). First, two critical parts of the OMT are designed separately, and then the overall optimization is carried out. In order to improve in-band impedance performance, stepped impedance matching rings are introduced into two orthogonal probes. An L-band quadruple-ridge waveguide OMT developed by this method is designed for FAST with reflection coefficient smaller than -20 dB for both polarizations, polarization coupling level lower than -43dB, and the insertion loss lower than 0. 15 dB over the entire operational bandwidth. The experimental results are in good agreement with the simulations. The design method proposed in this paper is suitable for the design of broadband quadruple-ridge waveguide OMT in various frequency ranges.