Satellite payloads are becoming much more complex with the evolution towards multimedia applications. Moreover satellite lifetime increases while standard and services evolve faster, necessitating a hardware platform that can evolves for not developing new systems on each change. The same problem occurs in terrestrial systems like mobile networks and a foreseen solution is the software defined radio technology. In this paper we describe a way of introducing this concept at satellite level to offer to operators the required flexibility of the system. The digital functions enabling this technology, the hardware components implementing the functions and the reconfiguration processes are detailed. We show that elements of the software radio for satellites exist and that this concept is feasible.