Extending the Field of View With Phased Array Techniques: Results of European SKA Research

The radio frequency window of the Square Kilometre Array is planned to cover the wavelength regime from centimeters up to a few meters. For this range to be optimally covered, different antenna concepts are considered. At the lowest frequency range, up to a few gigahertz, it is expected that multibeam techniques will be used, increasing the effective field-of-view to a level that allows very efficient detailed and sensitive exploration of the complete sky. Although sparse narrow-band phased arrays are as old as radio astronomy, multioctave sparse and dense arrays now considered for the SKA require new low-noise design, signal processing, and calibration techniques. The successful implementation of these new array techniques has already been introduced for the use of phased array feeds upgrading existing telescopes: enhancing aperture efficiency as well as effective field-of-view. Especially the development of low-cost array antenna design will allow a cost-effective large-scale implementation for the SKA. This paper addresses these new capabilities, emphasizing the R&D work done in Europe and aims to provide insight into the status of enabling technologies and technical research on polarization, calibration, and side-lobe control that will unleash the potential of phased arrays for future growth of radio astronomy synthesis arrays.