A 16-element LPDA random sparse prototype array for the SKA AA-mid instrument

The Square Kilometre Array - Aperture Array Mid-frequency instrument will be surveying the southern hemisphere skies with unprecedented sensitivity in the mid 2020s at frequencies from 400MHz up to the 21 cm Hydrogen line. The University of Cambridge is developing a sparse random array solution based on log-periodic dipole array antennas within the Aperture Array Design Consortium. This type of array provides increasing sensitivity with the wavelength, allowing the demanding sensitivity requirements of the Square Kilometre Array project to be met with 5 times fewer antennas then the competing dense regular array solutions. In this paper we present a 16-element prototype array built at our observatory at Lords Bridge, south of Cambridge, which will serve as a test bed for this technology. The array set-up, electromagnetic simulations and initial scattering parameter measurements are described.