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All-NbN SIS Mixers Using A Tuning Circuit With Two Half-Wavelength Distributed Junctions

Authors:
Y. Uzawa, A. Kawakami, M. Takeda, Z. Wang
Abstract:
A tuning circuit with two half-wavelength distributed junctions has been tested in quasi optical mixers using epitaxial NbN/MgO/NbN trilayers at frequencies above 700 GHz. The tuning circuit consisted of two half wavelength distributed NbN/MgO/NbN tunnel junctions connected in parallel by a half wavelength NbN/MgO/NbN microstrip line at a design center frequency of 870 GHz. The circuit was connected to the feed point of a center fed twin slot antenna by a quarter-wavelength impedance transformer. The mixer chips were installed in our quasi optical receiver system and their performances were measured. Preliminary results showed double-side-band receiver noise temperatures of 6-9 hfikB from 675 to 810 GHz for a mixer with the current density of only 6 kA/cm² (estimated [omega]CJRN product was about 30 at 750 GHz). The RF bandwidth was broader than that of a conventional full-wavelength distributed SIS mixer with the same current density. We are now redesigning and fabricating all-NbN SIS mixers to improve the performance at higher frequencies.
Categories:
SIS Mixers
Year:
2003
Session:
2
Full-text:
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Page Number(s):
63