Development of the sideband-separating receiver in 100-GHz band

tz receiver
We developed a new 2SB receiver system in the 100-GHz band for the 45-m telescope. Over the RF range of 80-120 GHz, the SSB receiver noise temperature of the mixer is lower than 100 K for the 4.0-8.0 GHz Intermediate Frequency (IF) band. The Image Rejection Ratios (IRRs) are greater than 10 dB over the same range. It is confirmed that the typical SSB receiver noise temperature of the new system is approximately half that of the previous systems of S80 and S100. The IF bandwidth of the new receiver system is 4 GHz for each IF output, while those of previous receivers are 600 MHz. We can detect 16 GHz in total. Using the newly developed 100-GHz band SIS receiver system for 45-m telescope, we observed the 12CO, 13CO and C18O emission lines simultaneously toward the Sagittarius B2 region in order to confirm the performance of the receiver system. This is the first astronomical observation using a waveguide-type dual-polarization sideband-separating SIS receiver system in the 100-GHz band. The SSB noise temperatures of the system, including the atmosphere, are approximately 180 K in the LSB at f_LO = 109 GHz (f_RF = 103 GHz) for pol-1 and at f_LO = 104 GHz (f_RF = 98 GHz) for pol-2 at an elevation of 80$^\circ$. The system noise temperature, including the atmosphere, became approximately half that of the previous receiver system (S100). The IRRs of the two 2SB mixers were calculated from the 12CO spectra at 115.271 GHz from the W51 giant molecular cloud, resulting in > 20 dB for one polarization and > 14 dB for the other polarization.


Reference
Nakajima, T. et al., "A New 100-GHz Band Front-End System with the Waveguide-Type Dual-Polarization Sideband-Separating SIS Receiver for the NRO 45-m Radio Telescope", Publ. Astron. Soc. Japan, 60, 435, 2008