A 200-300 GHz single sideband SIS mixer for radio astronomy

We present an ultra broadband low noise single sideband (SSB) SIS mixer developed for 200-300 GHz radio astronomy receivers. The mixer uses two Nb/AlO/sub x//Nb junctions. Image band rejection by 20 dB is provided in the entire 200-300 GHz band using a mechanical tuning of the single noncontacting backshort in the mixer. The SIS receiver SSB noise temperature is close to 50 K in the main part of the band. A speed-up of the observations at radio telescopes by a factor 2-3 is expected with the new receiver.