Measuring monopole and dipole polarizability of acoustic meta-atoms

We present a method to extract monopole and dipole polarizability from experimental measurements of two-dimensional acoustic meta-atoms. In contrast to extraction from numerical results, this enables all second-order effects and uncertainties in material properties to be accounted for. We apply the technique to 3D-printed labyrinthine meta-atoms of a variety of geometries. We show that the polarizability of structures with shorter acoustic path length agrees well with numerical results. However, those with longer path lengths suffer strong additional damping, which we attribute to the strong viscous and thermal losses in narrow channels

Fully Coherent UAV-based Near-Field Measurement and Transformation of the S67-15 m Ground Station Antenna at the German Space Operations Center in Weilheim

Abstract—Fully coherent unmanned aerial vehicle (UAV)-based near-field measurements of the S67 parabolic ground station antenna in Weilheim, Germany at 2.063 92 GHz are presented. The utilized measurement setup involves a vector network analyzer (VNA), radio frequency optical fiber connections, a laser tracking device (LT), and a specially designed light-weight dual-polarized Vivaldi antenna. The measurement data has been collected on a quasi-planar measurement surface in front of the reflector and the far-field patterns are obtained by field transformation from the irregular near-field data. Despite the complexity of this outdoor measurement setup with full exposure to varying weather conditions and the influence of the UAV on the near-field probe antenna, the far-field results show remarkable agreement with satellite based far-field measurement data