We have developed a wideband receiver system for simultaneous observations in CO lines of J = 2–1 and J = 3–2 transitions using the Osaka 1.85 m mm–submm telescope. As a frequency separation system, we developed multiplexers that connect three types of diplexers, each consisting of branch-line couplers and high-pass filters. The radio frequency (RF) signal is eventually distributed into four frequency bands, each of which is fed to a superconductor–insulator–superconductor (SIS) mixer. The RF signal from the horn is divided into two frequency bands by a wideband diplexer with a fractional bandwidth of $56\%$, and then each frequency band is further divided into two bands by each diplexer. The developed multiplexers were designed, fabricated, and characterized using a vector network analyzer. The measurement results showed good agreement with the simulation. The receiver noise temperature was measured by connecting the SIS-mixers, one of which has a wideband 4–21 GHz intermediate frequency (IF) output. The receiver noise temperatures were measured to be ∼70 K in the 220 GHz band, ∼100 K in the 230 GHz band, 110–175 K in the 330 GHz band, and 150–250 K in the 345 GHz band. This receiver system has been installed on the 1.85 m telescope at the Nobeyama Radio Observatory. We succeeded in simultaneous observations of six CO isotopologue lines with the transitions of J = 2–1 and J = 3–2 toward the Orion KL as well as on-the-fly mappings toward the Orion KL and W 51.

中文翻译：

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为大阪 1.85 m mm–submm 望远镜开发一种新的宽带外差接收器系统：接收器的开发和在 230 GHz 和 345 GHz 频段内使用具有 4-21 GHz IF 输出的 SIS 混频器同时观测的第一道曙光

我们开发了一个宽带接收器系统，用于使用大阪 1.85 m mm-submm 望远镜同时观测 J = 2-1 和 J = 3-2 跃迁的 CO 线。作为频率分离系统，我们开发了连接三种双工器的多路复用器，每种双工器都由支线耦合器和高通滤波器组成。射频 (RF) 信号最终被分配到四个频段，每个频段被馈送到超导体-绝缘体-超导体 (SIS) 混频器。来自喇叭的射频信号被一个分频带宽为$56\%$的宽带双工器分成两个频段，然后每个频段被每个双工器进一步分成两个频段。使用矢量网络分析仪设计、制造和表征开发的多路复用器。测量结果与仿真结果吻合良好。接收器噪声温度是通过连接 SIS 混频器来测量的，其中一个混频器具有宽带 4–21 GHz 中频 (IF) 输出。接收器噪声温度在 220 GHz 频带中测得约为 70 K，在 230 GHz 频带中约为 100 K，在 330 GHz 频带中为 110-175 K，在 345 GHz 频带中为 150-250 K。该接收器系统已安装在野边山射电天文台的 1.85 m 望远镜上。我们成功地同时观测了六条 CO 同位素线，其中 J = 2-1 和 J = 3-2 向猎户座 KL 的过渡以及向猎户座 KL 和 W 51 的动态映射。接收器噪声温度在 220 GHz 频带中测得约为 70 K，在 230 GHz 频带中约为 100 K，在 330 GHz 频带中为 110-175 K，在 345 GHz 频带中为 150-250 K。该接收器系统已安装在野边山射电天文台的 1.85 m 望远镜上。我们成功地同时观测了六条 CO 同位素线，其中 J = 2-1 和 J = 3-2 向猎户座 KL 的过渡以及向猎户座 KL 和 W 51 的动态映射。接收器噪声温度在 220 GHz 频带中测得约为 70 K，在 230 GHz 频带中约为 100 K，在 330 GHz 频带中为 110-175 K，在 345 GHz 频带中为 150-250 K。该接收器系统已安装在野边山射电天文台的 1.85 m 望远镜上。我们成功地同时观测了六条 CO 同位素线，其中 J = 2-1 和 J = 3-2 向猎户座 KL 的过渡以及向猎户座 KL 和 W 51 的动态映射。