  The very demanding requirements of the SKA-low instrument call for a
challenging antenna design capable of delivering excellence performance in
radiation patterns, impedance matching, polarization purity, cost, longevity,
etc. This paper is devoted to the development (design and test of first
prototypes) of an active ultra-wideband antenna element for the low-frequency
instrument of the SKA radio telescope. The antenna element and differential low
noise amplifier described here were originally designed to cover the former
SKA-low band (70-450MHz) but it is now aimed to cover the re-defined SKA-low
band (50-350MHz) and furthermore the antenna is capable of performing up to
650MHz with the current design. The design is focused on maximum sensitivity in
a wide field of view (+/- 45deg from zenith) and low cross-polarization ratios.
Furthermore, the size and cost of the element has to be kept to a minimum as
millions of these antennas will need to be deployed for the full SKA in very
compact configurations. The primary focus of this paper is therefore to discuss
various design implications for the SKA-low telescope.
