Fixed-Tuned Waveguide 0.6 THz SIS Mixer with Wide Band IF

Abstract

The Atacama Large Millimeter Array (ALMA) requires low noise SIS receivers for frequencies from about 80 GHz to 950 GHz with a very large IF bandwidth (8 GHz SSB upper or lower sideband, 8 GHz DSB or 4 GHz dual sideband, upper and lower sideband). Since there will be a large number of antennas in the array (currently 64), additional requirements such as high reliability, low cost, and the production of a relatively large number of mixers have to be addressed. In this paper we report the results of a waveguide mixer with a fixed backshort for ALMA band 9 (602 - 720 GHz). The mixer is based on standard Nb/A10,INb SIS junction technology. This mixer was tested with a wide band IF amplifier with and without isolator. Mixer measurement results for different LO frequencies across a wide IF band (4-8 GHz) will be presented. DSB Receiver noise across the both RE and IF band was measured, and receiver noise as low as 136 K at 650 GHz was demonstrated over the wideband IF. Finally, the possibility of a small production series of such a mixer is discussed with results on a first batch of mixer-blocks will be presented.