A 100 GHz Josephson mixer using resistively-shunted Nb tunnel junctions

The authors describe preliminary mixer results using resistively shunted Nb/AlO/sub x//Nb tunnel junctions in a 100-GHz waveguide mixer mount. The mixer utilizes robust, lithographically defined devices which have nonhysteretic I-V curves. A receiver temperature of 390 K (D5B) has been obtained with a conversion loss of -6.5 dB. The receiver's behavior agrees qualitatively with the behavior predicted by the resistively shunted junction model. Substantial improvements in performance are expected with the use of better-optimized shunted junctions and numerical simulations suggest that, if devices with higher I/sub C/R/sub N/ (critical-current normal-resistance) products can be obtained. Josephson effect mixers could be competitive with superconductor-insulator-superconductor (SIS) mixers at high frequencies.<
>