A Tuning Circuit with Two Half-Wave Distributed Junctions for All-NbN SIS Mixers |
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Authors: | Y. Uzawa M. Takeda A. Kawakami Z. Wang |
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Affiliation: | 1. Kansai Advanced Research Center Communications Research Laboratory, 588-2 Iwaoka, Iwaoka-cho, Nishi-ku Kobe, 651-2492, Japan.
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Abstract: | A novel broadband tuning circuit composed of two low-current-density half-wave NbN/MgO/NbN tunnel junctions connected by a half-wave NbN/MgO/NbN microstrip line has been successfully tested in a quasi-optical mixer at frequencies above 700 GHz. The circuit had a designed center frequency of 870 GHz, was integrated in a center-fed twin-slot antenna, and was fed via a quarter-wave impedance transformer. Heterodyne measurments showed double-side-band receiver noise temperatures equivalent to 6-9 quanta from 675 to 810 GHz for a mixer with a current density of 6.7 kA/cm2. The RF bandwidth was broader than that of a conventional mixer using a full-wave junction with the same current density. |
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