A Cost-Effective Tethered-UAV-Based Coherent Near-Field Antenna Measurement System

Abstract

For antenna measurements, the device under test (DUT) is usually transported to an anechoic chamber equipped with a scanner system. To measure on-site, unmanned aerial vehicles (UAVs) are a flexible solution as they can precisely maneuver a probe antenna over a surface in the DUT's near-field region. In this work, the designed multi-rotor UAV enables electromagnetically optimal placement of the probe antenna and effective gravity center re-balacing by payload position adjustment. The on-board software-defined radio (SDR) serves as a dual-channel receiver for the dual-polarized probe and as a signal source. For phase-coherent measurements, the source signal is transmitted to the DUT via an optical fiber tethering the UAV to the ground control station. Power supply cables allow unlimited flight times. A laser-based tracking system originating from virtual reality (VR) applications measures the probe position and orientation. The developed operator software guides the UAV along a trajectory and records the irregularly distributed near-field samples. An inverse equivalent sources solver (IESS) with full probe correction computes equivalent sources for antenna diagnostics and the DUT far field. The deployed components make the system very cost-effective. Still, verification measurements demonstrate its usability and the accuracy of the results for frequencies up to several GHz.