Recent advances in millimeter- and submillimeter-wave astronomy demand heterodyne receivers that simultaneously provide wide intermediate-frequency (IF) bandwidth and low receiver noise temperature. In this work, we present the design, fabrication, and experimental validation of a wide-IF (8–16 GHz) superconductor-insulator-superconductor (SIS) mixer for the 150 GHz band. The device employs a series array of four Nb/AlOx/Nb SIS junctions with a target RF embedding impedance near the optimum impedance of 31 Ω, and it is integrated with a pentagonal probe and a WR 6.5 waveguide for RF broadband coupling. Full-circuit simulations conducted in SuperMix were used to define the layout, and the performance of the fabricated mixer was evaluated in a 4 K test cryogenic receiver using hot/cold-load measurements over the 8–16 GHz IF band in double-sideband (DSB) mode. At a local oscillator (LO) frequency of 154 GHz, the mixer exhibits a maximum DSB conversion gain of 6 dB with a corresponding receiver noise temperature (Trx) ∼ 29 K. Across the IF band, Trx averages 43 K with a range of 25–76 K. These results establish the developed mixer as a promising candidate for next-generation wide-IF astronomical receivers.

Introduction
SIS Mixer Design and Fabrication
    Junction Parameter
    Junction Performance Analysis
    The Probe Antenna and the Mixer Mount Block
    RF and IF Circuits of the Mixer
    Simulation Results of Full Circuit for the SIS Mixer
    Mixer Fabrication
Experimental Results
    Receiver Noise Temperature
    Conversion Gain and Noise Temperature of Mixer
Discussion and Conclusion
References

• Jiman Kang(University of Science and Technology (UST), Daejeon 34113, Republic of Korea, Korea Astronomy and Space Science Institute (KASI), Daejeon 34055, Republic of Korea)
• Jung-Won Lee(University of Science and Technology (UST), Daejeon 34113, Republic of Korea, Korea Astronomy and Space Science Institute (KASI), Daejeon 34055, Republic of Korea) Corresponding author
• Wei-Chun Lu(Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), Taipei 10617, Taiwan)
• Ming-Jye Wang(Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), Taipei 10617, Taiwan)