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  • 1990-1994  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Dispersion in Nb microstrip transmission lines at submillimeter wave frequencies (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2712-2714 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the effects of dispersion on the resonant mode frequencies of open-ended Nb-SiOx-Nb microstrip transmission lines over a frequency range from 50 to 800 GHz. Submicron Nb/Al-AlOx/Nb Josephson junctions were used as both voltage-controlled oscillators and detectors to sample the high order modes of the resonators. The resonator modes are equally spaced up to about 550 GHz where the mode spacing start to decrease gradually to a minimum above the gap frequency fg≈700 GHz and then increases. Results are in good agreement with the expected theoretical behavior based on the Mattis–Bardeen conductivity of the superconductor line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108069
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A low-noise SIS receiver measured from 480 GHz to 650 GHz using Nb junctions with integrated RF tuning circuits (1994)
    Springer
    International journal of infrared and millimeter waves 15 (1994), S. 943-965 
    Details
    ISSN: 1572-9559
    Keywords: superconductors ; SIS junctions ; SIS mixers ; SIS receivers ; integrated tuning circuits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A heterodyne receiver using an SIS waveguide mixer with two mechanical tuners has been characterized from 480 GHz to 650 GHz. The mixer uses either a single 0.5 × 0.5 µm2 Nb/AlOx/Nb SIS tunnel junction or a series array of two 1 µm2 Nb tunnel junctions. These junctions have a high current density, in the range 8 – 13 kA/cm2. Superconductive RF circuits are employed to tune the junction capacitance. DSB receiver noise temperatures as low as 200 ± 17 K at 540 GHz, 271 K ± 22 K at 572 GHz and 362 ± 33 K at 626 GHz have been obtained with the single SIS junctions. The series arrays gave DSB receiver noise temperatures as low as 328 ± 26 K at 490 GHz and 336 ± 25 K at 545 GHz. A comparison of the performances of series arrays and single junctions is presented. In addition, negative differential resistance has been observed in the DC I–V curve near 490, 545 and 570 GHz. Correlations between the frequencies for minimum noise temperature, negative differential resistance, and tuning circuit resonances are found. A detailed model to calculate the properties of the tuning circuits is discussed, and the junction capacitance as well as the London penetration depth of niobium are determined by fitting the model to the measured circuit resonances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02096128
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    180–425 GHz low noise SIS waveguide receivers employing tuned Nb/AIO x /Nb tunnel junctions (1994)
    Springer
    International journal of infrared and millimeter waves 15 (1994), S. 783-805 
    Details
    ISSN: 1572-9559
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report recent results on a 20% reduced height 270–425 GHz SIS waveguide receiver employing a 0.49 µm2 Nb/AlO x /Nb tunnel junction. A 50% operating bandwidth is achieved by using a RF compensated junction mounted in a two-tuner reduced height waveguide mixer block. The junction uses an “end-loaded” tuning stub with two quarter-wave transformer sections. We demonstrate that the receiver can be tuned to give 0–2 dB of conversion gain and 50–80% quantum efficiency over parts of it's operating range. The measured instantaneous bandwidth of the receiver is ≈ 25 GHz which ensures virtually perfect double sideband mixer response. Best noise temperatures are typically obtained with a mixer conversion loss of 0.5 to 1.5 dB giving uncorrected receiver and mixer noise temperatures of 50K and 42K respectively at 300 and 400 GHz. The measured double sideband receiver noise temperature is less than 100K from 270 GHz to 425 GHz with a best value of 48K at 376 GHz, within a factor of five of the quantum limit. The 270–425 GHz receiver has a full 1 GHz IF passband and has been successfully installed at the Caltech Submillimeter Observatory in Hawaii. Preliminary tests of a similar junction design in a full height 230 GHz mixer block indicate large conversion gain and receiver noise temperatures below 50K DSB from 200–300 GHz. Best operation is again achieved with the mixer tuned for 0.5–1.5 dB conversion loss which at 258 GHz resulted in receiver and mixer noise temperature of 34K and 27K respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02096576
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    Paper (German National Licenses)
    Fulltext
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