Baryon acoustic oscillations from Integrated Neutral Gas Observations: Broadband corrugated horn construction and testing

TL;DR

The paper details the design, construction, and testing of broadband corrugated feed horns and polarizers for the BINGO radio telescope, aimed at measuring HI emission to study dark energy.

Contribution

It introduces novel construction methods for large broadband feed horns and polarizers, achieving low loss and clean beam profiles for the BINGO telescope.

Findings

Prototype horn has 0.15 dB insertion loss across the band.

Main beam is Gaussian with -25 dB sidelobes.

Septum polarizer effectively separates circular polarization.

Abstract

The Baryon acoustic oscillations from Integrated Neutral Gas Observations (BINGO) telescope is a 40-m~class radio telescope under construction that has been designed to measure the large-angular-scale intensity of HI emission at 980--1260 MHz and hence to constrain dark energy parameters. A large focal plane array comprising of 1.7-metre diameter, 4.3-metre length corrugated feed horns is required in order to optimally illuminate the telescope. Additionally, very clean beams with low sidelobes across a broad frequency range are required, in order to facilitate the separation of the faint HI emission from bright Galactic foreground emission. Using novel construction methods, a full-sized prototype horn has been assembled. It has an average insertion loss of around 0.15 dB across the band, with a return loss around -25 dB. The main beam is Gaussian with the first sidelobe at around $-25 dB. A septum polariser to separate the signal into the two hands of circular polarization has also been designed, built and tested.