A 500 GHz Quasi-Optical Slot Antenna SIS Mixer

Yoshinori Uzawa, Zhen Wang, Akira Kawakami

Jonas Stasys Zmuidzinas, Henry George LeDuc

A quasi-optical SIS mixer designed for efficient radiation coupling is described. The mixer uses a twin-slot antenna which has the advantages of a good beam pattern and a low impedance. The radiation and impedance characteristics of the antenna were obtained from a moment-matched calculation. 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 Omega , which allows micron-size junctions 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 frequency. 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.>

Yasutaka Serizawa, Yutaro Sekímoto, Mamoru Kamikura +2 more

Jonas Stasys Zmuidzinas

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.

Steve A. Torchinsky, C. T. Cunningham, Steven R. Davies

Michael C. Gaidis, M. Bin, D Miller +3 more

We report on the continuing development of submillimetre quasi-optical slot antenna SIS mixers, which use two-junction tuning circuits. Direct and heterodyne Fourier transform spectrometer measurements have been performed to compare device performance with predictions. Demonstrated double-sideband receiver noise temperatures of better than 540 K at 808 GHz make these SIS mixers substantially better than GaAs Schottky receivers for the astronomically important CI and CO transitions near 810 GHz.