Low-noise waveguide SIS mixer with NbN/AlN/NbN tunnel junctions tuned by an NbN/MgO/NbTiN microstrip circuit

The low-noise performance of a waveguide SIS mixer with NbN/AlN/NbN tunnel junctions and an NbN/MgO/NbTiN tuning circuit on an MgO substrate was demonstrated at frequencies above the gap frequency of Nb. To design the mixer, the complex refractive index of the MgO substrate was measured by using a T...

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Bibliographic Details
Published in:Superconductor science & technology 2009-07, Vol.22 (7), p.075015-075015p6
Main Authors: Takeda, Masanori, Shan, Wenlei, Kojima, Takafumi, Saito, Shingo, Kroug, Matthias, Uzawa, Yoshinori, Wang, Zhen
Format: Article
Language:English
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Summary:The low-noise performance of a waveguide SIS mixer with NbN/AlN/NbN tunnel junctions and an NbN/MgO/NbTiN tuning circuit on an MgO substrate was demonstrated at frequencies above the gap frequency of Nb. To design the mixer, the complex refractive index of the MgO substrate was measured by using a THz time-domain spectrometer. The superconductive properties of NbTiN films on MgO were examined in detail. An uncorrected receiver noise temperature of 262 K (DSB) at 820 GHz was achieved in an IF bandwidth of 4-12 GHz at a bath temperature of 4.2 K. By comparing the measured and calculated conversion gains, the loss in the NbN/MgO/NbTiN tuning circuit was estimated to be 0.98 dB at 810 GHz.
ISSN:0953-2048
1361-6668
DOI:10.1088/0953-2048/22/7/075015