We develop a radio receiver system operating at λ ~ 1.3 mm for the 6 m telescope of Seoul Radio Astronomy Observatory. It consists of a dual polarization receiver, a couple of IF processing units, two FFT spectrometers, and associated software. By adopting sideband-separating superconductor mixers with image band terminated to waveguide load at 4.2 K, we achieve TRX ≤ 100 K and Tsys less than 150 K at best weather condition over 210-250 GHz frequency range. The intermediate frequency signal of 3.5-4.5 GHz is down converted to 0-1 GHz and fed into the FFT spectrometers. The spectrometer covers 1 GHz bandwidth with a spectral resolution of 61 KHz. Test observations are conducted toward several radio sources to evaluate the performance of the system. Aperture and beam efficiencies measured by observing planets are found to be typically 44  59% and 47  61%, respectively over the RF band, which are consistent with those measured at 3 mm band previously.

ABSTRACT
1. INTRODUCTION
2. NEW FRONTEND
    2.1 Design Cencepts
    2.2 Sideband Rejection Implemented inWaveg-uide
    2.3 LO Circuit
    2.4 Receiver Optics
    2.5 Cryogenics
    2.6 Frontend Performances
3. IF CIRCUITS AND SPECTROMETERS
4. SOFTWARE
5. TEST OBSERVATION AND EFFICIENCY MEASUREMENTS
    5.1 Test Observation
    5.2 Efficiency Measurements
6. CONCLUSIONS
REFERENCES

• JUNG-WON LEE(Korea Astronomy and Space Science Institute) Corresponding Author
• CHANG-HEE KIM(Department of Physics and Astronomy, Seoul National University)
• HYUNWOO KANG(Korea Astronomy and Space Science Institute)
• BANGWON LEE(Department of Physics and Astronomy, Seoul National University)
• JUNGHWAN HAN(Department of Physics and Astronomy, Seoul National University)
• SEOK-HO LEE(Department of Physics and Astronomy, Seoul National University)
• IL-GYO JEONG(Department of Physics and Astronomy, Seoul National University)
• BON-CHUL KOO(Department of Physics and Astronomy, Seoul National University)
• YONG-SUN PARK(Department of Physics and Astronomy, Seoul National University)