On the Mobility Effect in UAV-Mounted Absorbing Metasurfaces: A Theoretical and Experimental Study.

In this work, we focus on the theoretical modeling and experimental evaluation of absorbing metasurfaces mounted on unmanned aerial vehicles (UAVs) as facilitators for secure wireless communication channels. Specifically, we present a network architecture based on UAV-mounted metasurfaces and conduct a comprehensive analysis of its components. Furthermore, by utilizing physical optics, namely the Fresnel-Kirchhoff diffraction formula, we develop a comprehensive path loss model that accurately calculates the scattering of wavefronts from metasurfaces with arbitrary configurations; this model enables the quantification of path loss and mobility effects, including pointing accuracy, misalignment, and UAV flying stability, for both near- and far-field conditions. Finally, experimental measurements are conducted using a state-of-the-art static absorbing metasurface and a commercial UAV in an anechoic chamber environment and close agreement between theoretical and experimental results, down to the radiative near-field region, is illustrated. Specifically, our findings indicate that absorbing metasurfaces can act as notch filters with minimal impact on pointing and positioning accuracy, exhibiting a 3 dB beamwidth of +/- 15 degrees compared to ideal static conditions.