Abstract

Cryogenically cooled receiver systems covering three millimetre-wave observing bands are being designed for the Australia Telescope National Facility Compact Array (ATCA), situated near Narrabri in northern New South Wales, Australia. The ATCA consists of six 22- metre dish antennas capable of operating up to 115 GHz. Millimetre-wave receiver systems covering the frequency ranges 16 to 26 GHz and 85 to 105 GHz have been installed. Future upgrades are planned to extend the upper frequency range to 115 GHz and to include coverage of the 30 to 50 GHz band. A range of monolithic microwave integrated circuits (MMICs) has been designed for the new millimetre-wave receiver systems. Indium phosphide MMIC low noise amplifiers in the front end are cryogenically cooled to 15 Kelvin to minimize their noise and maximise the sensitivity of the receiver system. Custom designed indium phosphide and gallium arsenide millimetre-wave MMIC mixers, power amplifiers and doublers are also used in the conversion and local oscillator systems.