Design of the New Wideband Vivaldi Feed for the HERA Radio-Telescope Phase II

This article presents the design of a new dual-polarized Vivaldi feed for the Hydrogen Epoch of Reionization Array (HERA) radio telescope. This wideband feed has been developed to replace the Phase I dipole feed and is used to illuminate a 14 m diameter dish. It aims to improve the science capabilities of HERA, by allowing it to characterize the redshifted 21 cm hydrogen signal from the Cosmic Dawn as well as from the Epoch of Reionization. This is achieved by increasing the bandwidth from 100–200 to 50–250 MHz, optimizing the time response of the antenna–receiver system and improving its sensitivity. This new Vivaldi feed is directly fed by a differential front-end module placed inside the circular cavity and connected to the back end via cables that pass in the middle of the tapered slot. We show that this particular configuration has minimal effects on the radiation pattern and the system response.