Development of a new wideband heterodyne receiver system for the Osaka 1.85 m mm–submm telescope: Receiver development and the first light of simultaneous observations in 230 GHz and 345 GHz bands with an SIS-mixer with 4–21 GHz IF output

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