The corrugated horn is a high-performance feed often used in radio telescopes. There has been a growing demand for wideband optics and corrugated horns in millimeter- and submillimeter-wave receivers as they improve observation efficiency and allow us to observe important emission lines such as CO in multiple excited states simultaneously. However, in the millimeter/submillimeter band, it has been challenging to create a conical corrugated horn with a fractional bandwidth of ∼60% because the wavelength is very short, making it difficult to make narrow corrugations. In this study we designed a conical corrugated horn with good return loss, low cross-polarization, and symmetric beam pattern in the 210–375 GHz band (56% fractional bandwidth) by optimizing the dimensions of the corrugations. The corrugated horn was installed on the Osaka 1.85 m mm–submm telescope with matched frequency-independent optics, and simultaneous observations of 12CO, 13CO, and C18O (J = 2–1, 3–2) were successfully made. We describe the new design of the corrugated horn and report the performance evaluation results including the optics.

中文翻译：

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为大阪 1.85 m mm-submm 望远镜开发新的宽带外差接收器系统：覆盖 210-375 GHz 频段的波纹喇叭和光学器件

波纹喇叭是射电望远镜中常用的高性能馈源。对毫米波和亚毫米波接收器中的宽带光学器件和波纹喇叭的需求不断增长，因为它们提高了观察效率，并使我们能够同时观察多个激发态的重要发射线，例如 CO。然而，在毫米/亚毫米波段，由于波长非常短，很难制造出部分带宽约为 60% 的锥形波纹喇叭，因此很难制造出窄波纹。在这项研究中，我们通过优化波纹的尺寸设计了一种在 210-375 GHz 频段（56% 部分带宽）内具有良好回波损耗、低交叉极化和对称波束图案的锥形波纹喇叭。瓦楞喇叭安装在大阪 1 号上。85 m mm-submm 望远镜与匹配的频率无关光学系统，成功地同时观测了 12CO、13CO 和 C18O（J = 2-1、3-2）。我们描述了波纹喇叭的新设计，并报告了包括光学元件在内的性能评估结果。