4. Conclusion

The development of spectrum monitoring and its components - technical analysis of signals, identification of transmitters, listening and analysis of decoded content - is fundamentally linked to that of radiocommunications itself, whether for spectrum monitoring in a civil regulatory context, or for battlefield surveillance in a tactical or strategic military context.

The communication signal analysis techniques required for radio surveillance are becoming increasingly complex and diversified:

• the signals to be processed are increasingly varied, versatile and stealthy, properties reinforced by the growing predominance of digital transmissions over analogue transmissions;

• signals, especially military ones, are becoming increasingly agile in frequency ;

• ...