L Band Phased Array Feed Noise Figure and Radiation Efficiency Measurement with the Antenna Y Factor Method

Abstract

The noise performance of a high sensitivity, wide-field astronomical phased array feed receiver can be characterized by measurements using the antenna Y factor method. These measurements are used to determine figures of merit for an active array receiver. Antenna elements for the Advanced L Band Phased Array Camera for Astronomy (ALPACA) were measured using the antenna Y factor method to determine the active array and receiver noise figure, the antenna loss, receiver equivalent noise temperature, and radiation efficiency of the system over its 500[Formula: see text]MHz operating bandwidth. The completed ALPACA instrument will feature a fully cryogenic design with both the low-noise amplifiers and array elements cryogenically cooled. The uncooled performance measurements from the antenna Y factor method are used to extrapolate the elements cryogenic radiation efficiency and antenna loss showing that it is expected that the elements will contribute less than 1 K to the overall system noise temperature. These results validate the antenna Y factor method to measure key antenna parameters such as the antenna radiation efficiency and show that the instruments front-end array and electronics meets expected performance targets.

First Extragalactic Detection of Thermal Hydroxyl (OH) 18 cm Emission in M31 Reveals Abundant CO-faint Molecular Gas

“…Unfortunately, single-beam L-band (centimeter) instruments would potentially require a prohibitive amount of time to survey Local Group galaxies at the 18 cm OH lines. New multibeam phased array feeds (e.g., Roshi et al 2018;Pingel et al 2021;Burnett et al 2023) will drastically improve mapping speeds for large single-dish telescopes by orders of magnitude. In the near future, these instruments will be able to ).…”