Comparison of horn antenna geometries for the RHINO 21cm global signal experiment

Abstract

The detection and mapping of the Global 21cm Hydrogen Signal is one of the most promising and exciting areas of study within cosmology and astronomy as whole. Since the detection of the Cosmic Microwave Background by accident in 1964 the 21cm signal has been thought of as a viable pathway into probing the early timescales of our Universe. The unanticipated detection of the CMB was made by Penzias and Wilson using a horn shaped radio antenna. The high gain and low noise properties of the horn antenna proved crucial in achieving observational data for the CMB so it is hypothesized that a horn shaped antenna may be useful in the pursuit of an unequivocal detection of the Global 21cm Hydrogen Signal. In this Masters Thesis this hypothesis is investigated in collaboration with the RHINO Horn project, by first designing a wide range of horn antenna within MATLAB to determine which type of horn antenna would be best suited to attempt to make this measurement. The antenna beam patterns were run through python simulations of diffuse sky emission and their respective sky response temperatures were analysed alongside their frequency dependency. The results of the simulations showed that MATLAB displayed numerical convergence issues with the more complex antenna designs: the potter horn and corrugated horns, it was determined that a more geometrically complex design suite would be more suitable for these particular antenna. Despite this the analysis still showed the potter horn having the highest average antenna temperature (457.5K) at 70MHz over a 12 hour observation period followed closely by the standard pyramidal design (414.5K). The frequency dependence test involved carrying out an eigendecompostion on the frequency-frequency covariance matrix for each set of simulated data. These results showed a correlation between the maximum gain of an antenna beam and how dependent on frequency the antenna was, i.e. as the gain increased the frequency dependency lessened, with the corrugated conical horn antenna having the least frequency dependency.

Date of Award	14 Feb 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Phil Bull (Main Supervisor) & Eamonn Kerins (Co Supervisor)