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

TL;DR

This paper introduces a new wideband dual-polarised Vivaldi feed for the HERA radio-telescope, significantly enhancing its bandwidth, sensitivity, and ability to study cosmic hydrogen signals.

Contribution

It presents the design and implementation of a novel Vivaldi feed that replaces the previous dipole, expanding bandwidth and improving system performance for cosmic signal detection.

Findings

Bandwidth increased from 100-200 MHz to 50-250 MHz

Radiation pattern remains stable with new design

Enhanced sensitivity and time response

Abstract

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. 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 which pass in the middle of the tapered slot. We show that this particular configuration has minimal effects on the radiation pattern and on the system response.