Applications of mm-wave SIS mixers to middle atmosphere monitoring systems

We have already developed a low-noise 100 GHz band (98-115 GHz) SIS mixer using Nb/AlOx/Nb junction technology. The mixer has a noise temperature of 17 K when used as a double sideband (DSB) heterodyne receiver. The SIS receiver has been in use in the 4 m radio telescope at Nagoya University for five years. As a further application of the SIS mixer, we developed middle-atmosphere ozone monitoring system using an SIS mixer for the first time. The system can measure ozone mixing ratio every 5 minutes. The integration time is less than 1/10 of the time needed in a conventional system using Schottky barrier diode (SBD) mixers. We have also begun developing developing a 200 GHz band (210-280 GHz) SIS mixer for radio astronomy and for monitoring other minor constituents such as ClO. The preliminary experiment showed that the mixer has a rather low noise temperature of 60 K (DSB).<>