We detail the the REACH radiometric system designed to enable measurements of the 21-cm neutral hydrogen line. Included is the radiometer architecture and end-to-end system simulations as well as a discussion of the challenges intrinsic to highly-calibratable system development. Following this, we share laboratory results based on the calculation of noise wave parameters utilising an over-constrained least squares approach demonstrating a calibration RMSE of 80 mK for five hours of integration on a custom-made source with comparable impedance to that of the antenna used in the field. This paper therefore documents the state of the calibrator and data analysis in December 2022 in Cambridge before shipping to South Africa.
@article{arxiv.2307.00099,
title = {Receiver design for the REACH global 21-cm signal experiment},
author = {Ian L. V. Roque and Nima Razavi-Ghods and Steven H. Carey and John A. Ely and Will Handley and Alessio Magro and Riccardo Chiello and Tian Huang and P. Alexander and D. Anstey and G. Bernardi and H. T. J. Bevins and J. Cavillot and W. Croukamp and J. Cumner and E. de Lera Acedo and D. I. L. de Villiers and A. Fialkov and T. Gessey-Jones and Q. Gueuning and A. T. Josaitis and G. Kulkarni and S. A. K. Leeney and R. Maiolino and P. D. Meerburg and S. Mittal and M. Pagano and S. Pegwal and C. Pieterse and J. R. Pritchard and A. Saxena and K. H. Scheutwinkel and P. Scott and E. Shen and P. H. Sims and O. Smirnov and M. Spinelli and K. Zarb-Adami},
journal= {arXiv preprint arXiv:2307.00099},
year = {2025}
}