Nuevos sistemas de medida basados en sensores electromagneticos embarcados en vehículos aéreos no tripulados para aplicaciones de subsurface imaging y medida de antenas"- "novel measurement systems based on electromagnetic sensors on board unmanned aerial vehicles for subsurface imaging and antenna measurement applications

Résumé

ABSTRACT (ENGLISH): This thesis presents two novel measurement systems based on mounting electromagnetic sensors working at microwave frequencies on board Unmanned Aerial Vehicles (UAVs). The ability of inspecting difficult-to-access areas without interacting with the environment is one of the reasons that have contributed to widely increase the usage of UAVs in the field of Non-Destructive Testing (NDT). In particular, the systems developed and patented in the framework of this thesis are devoted to two main fields of application: subsurface radar imaging and antenna measurement at operational conditions. These kinds of applications have been given the name of beyond-the-visible applications, since the capability of penetration in opaque media of the on-board sensors allows the detection of phenomena that could not be detected with optical systems. Concerning subsurface imaging, a Ground Penetrating Radar (GPR) has been integrated into the UAV. The primary application of this prototype is the detection of explosive hazards buried below the soil, such as Improvised Explosive Devices (IEDs). Therefore, the goal of this system is to provide radar images of the inspected soil and the objects buried below its surface. These images are obtained by coherently combining the radar measurements with a Synthetic Aperture Radar (SAR) method. Furthermore, this method is complemented with other techniques in order to estimate the soil composition and to mitigate the clutter. Regarding antenna measurement, a power detector has been mounted on board the UAV to gather amplitude-only data in the Near-Field (NF) region of the Antenna Under Test (AUT). These measurements are post-processed using the Phaseless Sources Reconstruction Method (PSRM), which is a phase retrieval technique able to estimate an equivalent currents distribution at a surface enclosing the AUT. This distribution provides antenna diagnostics information and it can be used to calculate the Far-Field (FF) radiation pattern.