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

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This paper presents the design of a new dual-polarised 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 characterise 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 MHz to 50 -- 250 MHz, optimising the time response of the antenna - receiver system, and improving its sensitivity.