A multibeam SIS mixer module for a focal plane array receiver

The integration of many receiver units into a receiver array is a common me thod of improvement of imaging systems. This approach, well known in the mm band for Schottky mixer arrays, has not so far been developed for Supercon ductor - Insulator - Superconductor (SIS) junction mixers, which give the b est sensitivity in the short mm wave range and in the submm range. We demonstrate for the first time a practical low noise multibeam receiver module using SIS mixer technology. The basis for :he integration of several SIS mixers with a common local oscillator source is given by the saturatio n of the SIS receiver noise dependence upon local oscillator power. The mod ule comprises three identical SIS mixers integrated with a common local osc illator, coupled through a three branch waveguide directional coupler. The multibeam module has been developed for a focal plane array receiver of the 30 meter radio telescope of the Institut de Radioastronomie Millimetrique (IRAM).