Title :
Quasi-optical slot antenna SIS mixers
Author :
Zmuidzinas, Jonas ; LeDuc, H.G.
Author_Institution :
George W. Downs Lab. of Phys., California Inst. of Technol., Pasadena, CA, USA
fDate :
9/1/1992 12:00:00 AM
Abstract :
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 Ω, 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
Keywords :
Josephson effect; aluminium compounds; antenna radiation patterns; electric impedance; electron device noise; microstrip antennas; microwave integrated circuits; mixers (circuits); niobium; strip line components; submillimetre wave devices; superconducting junction devices; 490 to 500 GHz; Josephson effect; MIC; Nb-AlOx-Nb; SIS mixers; THF; impedance characteristics; magnetic field; micron-size junctions; mixer saturation power; moment-matched calculation; quasi-optical mixer; radiation coupling; superconducting microstrip transmission lines; tapered lines; tunnel junction; twin-slot antenna; Couplings; Impedance; Magnetic field measurement; Magnetic noise; Microstrip antennas; Niobium; Slot antennas; Superconducting device noise; Superconducting films; Superconducting transmission lines;
Journal_Title :
Microwave Theory and Techniques, IEEE Transactions on
