Direction-finding applications can be found in both the civilian and military sectors. The main applications include distress signal search, self-guided navigation and radio spectrum monitoring. For the first two applications, the direction finder needs to be on-board. In this case, the sensor needs to be small to reduce its size and weight.

In the context of on-board antennas on small carriers such as small satellites or UAVs, for example, it is vital that the sensor takes up very little space. Conventional direction-finding is based on the principle of interferometry, requiring the use of a large antenna array to improve angular resolution. Another approach is based on the use of a vector antenna exploiting polarization diversity. This implies a smaller sensor with lower angular resolution performance. However, a broadband multi-access vector sensor benefits from additional degrees of freedom to improve performance through antenna processing techniques using frequency and radiation pattern diversity.

The aim of this work is both to design a small-scale broadband vector sensor, and to develop innovative antenna processing that can exploit polarization, frequency and possibly time information to extend source localization (angle-of-arrival detection) to positioning (distance estimation).