Sideband-separating MMIC receivers for observation in the 3-mm band

摘要

Wideband receivers for the 3-mm band were developed for CARMA, the Combined Array for Research in Millimeterwave Astronomy. Three cryogenic MMIC (monolithic microwave integrated circuit) amplifiers manufactured in InP 35- nm technology are combined in a block with waveguide probes and gain equalizers to cover the 80–116 GHz band. These are followed by a sideband-separating mixer that has two 17 GHZ wide outputs, for upper and lower sidebands. Each receiver has a feed horn followed by a circular-to-linear polarizer and orthomode transducer. The two polarizations are amplified by the cryogenic MMICs, and the outputs downconverted in sideband separating mixers, resulting in four 1–18 GHz channels that can be simultaneously correlated. The first receiver was tested in the lab, and on-sky tests conducted at CARMA. Measured noise temperatures were in the range 40–70 K, with a sideband rejection of about 15 dB.