A study of the square kilometre array low-frequency aperture array

Thesis

This thesis primarily comprises simulations of SKA1-Low, the low-frequency aperture array of the Square Kilometre Array (SKA) radio telescope. Simulations assess how different design specifications would affect the telescope's performance and ability to undertake one of its key science projects: observing the Epoch of Reionisation (EoR). The simulations are based on the previous baseline design of ∼ 260 000 dipole antennas in 1024 stations of 256 antennas each.

It is found that errors in the gain and phase of signals at each antenna can significantly affect observations, with the greatest impact at the lowest frequencies. The EoR signal will be detectable at limited redshifts with gain errors of 10% and phase errors of 6 degrees, however to ensure the systematic noise contribution from these errors is always weaker than the EoR signal between z ∼ 10 − 21 and spherical harmonic multipole coefficients l ∼ 10² − 10⁴ , the gain and phase errors may need to be less than or equal to approximately 5 × 10⁻⁶ and less than or equal to approximately 3 × 10⁻⁴ degrees, respectively.

Alternative telescope layouts to the SKA1-Low baseline design of 1024 stations containing 256 antennas each are evaluated. Some telescope models which share antennas between stations, allowing stations to be formed in a flexible manner, are found to provide superior thermal noise sensitivity than the current design, but suffer greater detrimental effects from gain and phase errors when imaging.

The implementation of the digital signal processing of a station beamformer is also discussed. Calculations show that five or nine Field Programmable Gate Arrays (FPGAs) with specifications comparable to the Virtex UltraScale+ XCVU13P could be used to beamform a single 256-antenna SKA1-Low station, depending on the utilisation rate of the FPGAs and the number of channels required.

Authors: Sinclair, D; Jones, M

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: SKA; Beamformer; Square Kilometer Array; Beam former; Beamforming; Square Kilometre Array; Phased array; Aperture array; Interferometry; Beam forming
• Subjects: Astrophysics; Radio telescopes