Aperture array for low frequency: The vivaldi solution

Among the various technologies, sparse Aperture Array for Low frequency (AA-Low) are the system operating between 50-450MHz, that will be installed for the first receiving portion of SKA. This paper presents the Italian experiences and results concerning that field as part of the AADCC (Aperture Array Design Construction Consortium) with particular reference to the technology of the sensor type "Vivaldi".