Towards sideband-separation for ALMA's highest bands

Over the last few years, we developed high-performance sideband- separating (2SB) mixers for 600-720 GHz (Band 9) and 790-950 GHz (Band 10). The former have successfully been commissioned in the SEPIA front- end at APEX. On-sky image rejection ratios in excess of 24dB have been recorded for the CO(6-5) line at 691 GHz and the water maser line at 658 GHz, while lab testing shows 15dB or better over an extended RF band of about 580-740GHz. Noise temperature is better than 200K (SSB) over most of the band. The receiver cartridge has four 4-12 GHz IF outputs and is fully ALMA-frontend compatible. We intend to extend the IF bandwidth even further in the near future. The new Band 790-950 GHz 2SB mixer (intended for the FLASH front-end at APEX) has been tested in the lab recently and shows comparable performance characteristics. We see these mixers, with circulator-less wideband IF infrastructure, as an attractive upgrade for the highest ALMA bands.