A Sparse Near-Field Measurement Technology for SKA-Low Antenna System

The Square Kilometre Array low-frequency (SKA-Low) radio telescope is a project based on low-frequency (50–350 MHz) phased array of log-periodic antennas. As an international scientific project, its construction and operation will explore some of the open major scientific issues and challenges in the universe such as verification of the general relativity and mathematical models for dark energy and gravity, and close observation of galaxies among many others. However, due to its huge size (order of km) on-site measurements are necessary to verify the intended array performances. In this article, we propose a sparse near-field (NF) measurement method based on quantifying the autonomous aerial vehicle (AAV) trajectory offset error for SKA-Low array measurements sparse scanning is achieved by AAV equipped with microcrystal oscillators and lightweight probe. Compressed sensing restores the sparse scanning data to NF scanning data satisfying Nyquist’s sampling theorem. Subsequently, phaseless planar near-field-to-far-field transformation (NFT) is performed to achieve sparse NF measurement. The experimental results show that NFT using the data of recovering sparse matrices using a compressed sensing algorithm based on phaseless NF measurements is in high accordance with the results simulated. In a clean electromagnetic environment, on-site measurements were carried out on the SKA-Low array and the test results also proved the effectiveness of this method.