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Spectral performance of SKA log-periodic antennas I: Mitigating spectral artefacts in SKA1-LOW 21 cm cosmology experiments

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Authors
de Lera Acedo, E.
Trott, Cathryn
Wayth, Randall
Fagnoni, N.
Bernardi, G.
Wakley, B.
Koopmans, L.
Faulkner, A.
bij de Vaate, J.
Date
2017
Type
Journal Article

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de Lera Acedo, E. and Trott, C. and Wayth, R. and Fagnoni, N. and Bernardi, G. and Wakley, B. and Koopmans, L. et al. 2017. Spectral performance of SKA log-periodic antennas I: Mitigating spectral artefacts in SKA1-LOW 21 cm cosmology experiments. Monthly Notices of the Royal Astronomical Society. 469 (3): pp. 2662-2671.
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Monthly Notices of the Royal Astronomical Society
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Curtin Institute of Radio Astronomy (Physics)
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This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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Abstract

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 analysed 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 Radioastronomy Observatory, Western Australia in 2015 September 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.