Design of active waveguide OMT for radio astronomy receiver array in the 3 mm band

We describe the design of an integrated cryogenic receiver module based on an ""active"" waveguide Orthomode Transducer (OMT) for dual-polarization radio astronomy observations across 75-116 GHz (3-mm band). The receiver module consists of passive and active sections that can be incorporated in a very compact mechanical assembly suitable for integration in a focal plane array. The passive section of the receiver module employs a broadband backward-coupler waveguide OMT while the active section consists of ultra-low noise MMIC (Monolithic Microwave Integrated Circuit) amplifiers.