An S-band cryogenic phased array feed for radio astronomy

We describe the design and ground testing of a prototype S-band cryogenic phased array feed. The feed uses 6-mm thick solid aluminium Vivaldi antennas, which were designed using a commercial electromagnetic simulation software. The antennas are designed for easy removal and 40 of them have been integrated into an array. The return loss, inter element coupling and beam patterns have been tested at room temperature and found to agree with simulations. For cryogenic testing the array has been combined with an existing analogue receiver chain and integrated into an cryostat. When tested at 30 K in aperture array mode the system was found to possess a minimum receiver temperature of 12 K. Increasing the number of elements and combining the array with a beamformer would make it a suitable phased array feed (PAF) for radio-astronomy applications.