The Band 3 receiver (84-116 GHz) for ALMA

Abstract

Test results are presented of the Band 3 module integrated into the Atacama large millimeter array (ALMA) front end receiver. The 84 to 116 GHz collected signal by the Band 3 receiver is split into two orthogonal polarisations using an orthomode transducer and then down-converted to 6 GHz over 4 GHz bandwidth using sideband separating mixers with better than 10 dB of image rejection. The single sideband system's low noise of 35 to 45 K is achieved by cascading superconductor-insulator-superconductor (SIS) mixers and low noise cryogenic amplifiers that consist of three stage high mobility transistors (HEMT) operating at 4 K.