Quasi-optical Slot Antenna SIS Mixers

Jonas Stasys Zmuidzinas

Published Feb 1, 1991• 5 citations

Abstract

Abstract-We describe a new quasi-optical SIS mixer de-signed for efficient radiation coupling. The mixer uses a twin-slot antenna which has the advantages of a good beam pattern and a low impedance. The radiation and impedance character-istics of the antenna were obtained from a moment-method cal-culation. Tapered superconducting microstrip transmission lines are used to carry the radiation from the slot antennas to the tunnel junction. The effective impedance seen by the tunnel junction is quite low, about 4 R, which allows micron-size junc-tions to be used at 500 GHz. The mixers have been fabricated using Nb/Al-oxide/Nb tunnel junctions and a receiver noise temperature of 420 K (DSB) was measured at 490 GHz, which is the best yet obtained for a quasi-optical mixer at this fre-quency. The comparatively large junction area increases the mixer saturation power and allows strong suppression of noise from the Josephson effect by the application of a magnetic field of modest strength. I.

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