Performance of the First Three Preproduction 35-50 GHz Receiver Front-ends for Atacama Large Millimeter / submillimeter Array

The Band-1 receiver front-end cartridges for Atacama Large Millimeter Array, which covered 35 - 50 GHz frequency range, are now in preproduction stage. For the first three preproduction cartridges, the measured receiver noise temperature is less than 16-31K for any combination of the in band RF and LO frequencies. The measured gain flatness, even with the limitation of the optical window of the cryostat and the broadband matching of the cryogenic amplifiers, is typically lower than 5 dB over any 2GHz window. Extracted aperture beam efficiency is typically higher than 80% over the full frequency range. The crosstalk over the orthogonal channel is lower than -63 dB. For the suppression of the unwanted lower sideband, the imaged band suppression is higher than 20 dB for the worst case and around 30 dB typically.