1. INAF, Astrophysical Observatory of Arcetri; Florence Italy
2. INAF, Observatory of Radio Astronomy; Bologna Italy
3. CNR, Institute of Electronics, Computer and Telecommunication Engineering; Turin Italy
4. Polytechnic of Turin, Department of Environment, Land and Infrastructure Engineering; Turin Italy
5. INAF, Observatory of Radio Astronomy; Cagliari Italy
6. INAF, Catania Astrophysical Observatory; Gravina di Catania Italy
7. Department of Electrical, Electronic and Information Engineering; University of Bologna; Bologna Italy