7. Conclusion

Whether it's spectrum monitoring in a civilian context, regulation or battlefield surveillance in a tactical military context, or strategic intelligence, the evolution of spectrum radiosurveillance and its direction-finding and localization components is fundamentally linked to that of radiocommunications networks themselves, and the increasingly dense and complex radio environments they create.

To meet today's radiomonitoring requirements, the direction-finding and localization techniques used must be highly efficient:

• the signals to be processed are increasingly broadband, stealthy and agile in wide frequency ranges, a trend that has been greatly reinforced with the predominance of digital over analog transmissions;

• multiple accesses by several communication terminals on the same...