Wideband single pixel feed system over 4.6–24 GHz for the Square Kilometre Array

Abstract

We present the Band B feed system over 4.6-24 GHz designed for the Square Kilometre Array (SKA) reflector for radio astronomy applications. The feed is a Quad-ridge Flared Horn (QRFH) with a customized shape based on spline-defined profiles to achieve improved wideband performance. The feed system shows high aperture efficiency and sensitivity on the SKA reflector in predictions based on measured feed beam patterns. We present the feed design overview, cryogenic dewar concept and measurement of receiver noise (10-20 K) with wideband lownoise amplifiers, and full system simulation of the performance.Index Terms-quad-ridge flared horn, ultra-wideband feed, spine-defined profile, radio astronomy, sensitivity.

A 10:1 Bandwidth Cryogenic Quadruple-Ridged Flared Horn Design for Reflector Antennas in Radio Astronomy

“…The designed aperture of the QRFH feed is only 170 mm, which helps to reduce the size of the vacuum window and thermal load, and minimizes the cryostat volume to reduce the overall radiating surface area. An essential aspect of the important aspect cryogenic feed design is to assess its performance when it is placed inside the cryostat and being cooled down to the baseline requirement temperature of 45 K which meets the target of less than 50 K [1], [14].…”

“…Therefore, radio telescopes not only need to carefully design the feed, but also often reduce the internal noise of the system through refrigeration. According to WBSPF baseline of an internal report for Cryogenic feed, to reduce the ohmic loss to 0.08 dB, the physical temperature needs to be cooled to less than 50 K, and the estimated noise temperature for feed should be less than 0.94 K [1], [14]. This design criterion imposes further challenges in designing the SKA feed.…”