Development of the HIFI band 3 and 4 mixer units

We describe the current status of the HIFI mixer units for Band 3 and Band 4. The mixer units cover the 800-960 GHz and 960-1120 GHz frequency range and have a 4-8 GHz IF frequency band. The major requirements and the design strategy are described. Functional tests of the magnet, the de-flux heater, IF-circuit, and the corrugated horn were performed. Details of the design of the mixer units and the performance status are presented. The DSB receiver noise performance ranges from 210 K at 850 GHz to 430 K at 1075 GHz.Kavli Institute of NanoscienceApplied Science