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  • 1
    Electronic Resource
    Electronic Resource
    An SIS waveguide heterodyne receiver for 600 HGz-635 GHz (1994)
    Springer
    International journal of infrared and millimeter waves 15 (1994), S. 349-368 
    Details
    ISSN: 1572-9559
    Keywords: superconductors ; SIS junctions ; SIS mixers ; SIS receivers ; submillimeter waves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A waveguide SIS heterodyne receiver using a Nb/AlOX/Nb junction has been built for astronomical observations of molecular transitions in the frequency range 600 GHz - 635 GHz, and has been successfully used at the Caltech Submillimeter Observatory (CSO). We report double sideband (DSB) receiver noise temperatures as low as 245 K at 600 GHz -610 GHz, and near 300 K over the rest of the bandwidth. These results confirm that SIS quasiparticle mixers work well at submillimeter-wave frequencies corresponding to photon energies of at least 90% of the superconductor energy gap. In addition, we have systematically investigated the effect on the receiver performance of the overlap between first-order and second-order photon steps of opposite sign at these frequencies. The receiver noise increases by as much as 40% in the region of overlap. We infer potential limitations for operating submillimeter-wave Nb/AlOx/Nb mixers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02096246
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    Paper (German National Licenses)
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  • 2
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    Slot antenna SIS mixers for submillimeter wavelengths (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: We are developing improved versions of a slot antenna SIS mixer which we have previously described. The initial work demonstrated a double sideband noise temperature of 420 K for a 500 GHz quasi-optical SIS mixer employing a twin-slot antenna on a quartz dielectric substrate. A quartz hyperhemispherical lens is used to focus the incoming radiation onto the twin-slot antenna. The advantages of a twin-slot antenna include a low impedance (35 omega) and a clean, symmetric beam pattern into the dielectric with a 70 percent efficiency. In our original mixer, the radiation was coupled from the two slot antennas onto superconducting microstrip lines which fed the SIS junction. By performing an impedance transformation using tapered lines and by feeding the radiation from the two slots to the junction in parallel, the effective (real) impedance seen by the junction was reduced to just 4 omega. This very low impedance allowed a junction area of 2.3 sq micron to be used at 500 GHz, which was manufactured using optical lithography. However, no attempt was made to tune out the junction capacitance. We estimate that this capacitance reduces the impedance coupling efficiency to eta(sub Z) approx. equals 0.23, for our junction with omega R(sub N) C = 5.3 at 500 GHz. The recent development of techniques using electron-beam lithography to manufacture junctions with very small areas (approx. equals 0.1 sq microns) now allows considerably more flexibility in the design of SIS mixer circuits. We have redesigned the slot-antenna mixer to take advantage of this possibility. In particular, we have included a novel circuit which allows the junction capacitance to be tune out over a broad bandwidth. For instance, mixers designed for 800 GHz using NbN/MgO/NbN junctions with realistic parameters achieve a 3 dB impedance bandwidth of nearly 400 GHz. Furthermore, our circuit uses only short lengths of microstrip and should be less sensitive to RF losses than other designs. The improved impedance match should give a large reduction in noise temperature as compared to our previous mixer. The new devices are currently under fabrication. Further details of the design and any available experimental results are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Michigan Univ., The Third International Symposium on Space Terahertz Technology: Symposium Proceedings; p 234
    Format: text
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  • 3
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    Wideband fixed-tuned SIS receiver for 200-GHz operation (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We report on the design and development of a heterodyne receiver, designed to cover the frequency range 176-256 GHz. This receiver incorporates a niobium superconductor-insulator-superconductor (SIS) tunnel junction mixer, which, chiefly for reasons of reliability and ease of operation, is a fixed-tuned waveguide design. On-chip tuning is provided to resonate out the junction's geometric capacitance and produce a good match to the waveguide circuit. Laboratory measurements on the first test receiver indicate that the required input bandwidth (about 40%) is achieved with an average receiver noise temperature of below 50 K. Mixer conversion gain is observed at some frequencies, and the lowest measured receiver noise is less than 30 K. Furthermore, the SIS mixer used in this receiver is of simple construction, is easy to assemble and is therefore a good candidate for duplication.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Microwave Theory and Techniques. Symp. on Space Terahertz Technology - May 1994 at the Univ. of Michigan, Ann Arbor. (ISSN 0018-9480); 43; 4, pt. 2; p. 933-937|International Symposium on Space Terahertz Technology. Part 2; May 01, 1994; Ann Arbor, MI; United States
    Format: text
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