Cryogenic Performance of a Very Low Noise MMIC Ka-Band Radiometer Front-End

Radio telescopes have traditionally used a single receiver at the focus, effectively giving a one-pixel image of the sky. The One Centimetre Receiver Array (OCRA) is a three-stage programme to develop multi-pixel arrays to be mounted at the focus of large radio telescopes. OCRA-f is the second phase, funded under the EU FARADAY project, and consists of a 10-beam array installed on a 32-metre radio telescope in Poland. It will produce Ka-band radio maps of the sky, acting as a ten-pixel radio camera. The paper describes a state-of-the-art all-MMIC receiver front-end developed using the lattice-matched indium phosphide foundry process of NGST, California. The effect of leakage on system noise temperature is described. Finally measurements are presented yielding an overall noise temperature of less than 21 kelvin over a 10 GHz bandwidth at Ka band.