14 research outputs found
Spectral performance of SKA log-periodic antennas I: Mitigating spectral artefacts in SKA1-LOW 21 cm cosmology experiments
This paper is the first in a series of papers describing the impact of
antenna instrumental artefacts on the 21-cm cosmology experiments to be carried
out by the low frequency instrument (SKA1-LOW) of the Square Kilometre Array
telescope (SKA), i.e., the Cosmic Dawn (CD) and the Epoch of Reionization
(EoR). The smoothness of the passband response of the current log-periodic
antenna being developed for the SKA1-LOW is analyzed using numerical
electromagnetic simulations. The amplitude variations over the frequency range
are characterized using low-order polynomials defined locally, in order to
study the impact of the passband smoothness in the instrument calibration and
CD/EoR Science. A solution is offered to correct a fast ripple found at 60~MHz
during a test campaign at the SKA site at the Murchison Radio-astronomy
Observatory, Western Australia in September 2015 with a minor impact on the
telescope's performance and design. A comparison with the Hydrogen Epoch of
Reionization Array antenna is also shown demonstrating the potential use of the
SKA1-LOW antenna for the Delay Spectrum technique to detect the EoR