An Application of CG-NUFFT to UAV-Based Amplitude-Only Near-Field Antenna Testing

Unmanned aerial vehicles (UAVs) have gained attention in antenna near-field measurements for outdoor large antennas due to their ability to reduce the amount of required test equipment. The most promising UAV-based setup for these outdoor measurements is an amplitude-only approach as amplitude-only measurements are robust against positioning errors which is an inherent problem facing UAVs. Current implementations of UAV amplitude-only near-field scans utilize matrix solvers and equivalent currents to account for the non-uniform data collection when performing phase reconstruction. In this paper, the conjugate gradient non-uniform fast Fourier transform (CG-NUFFT) algorithm is utilized for phase reconstruction from non-uniform two planar amplitude-only measurements. The system is tested through simulations of a dipole-element phased array antenna with various tapering and steering angles, aiming to reconstruct the far-field patterns. UAV non-uniform positioning is also simulated by introducing deviations to the targeted uniform waypoints. Simulation results demonstrate that the CG-NUFFT algorithm accurately reconstructs far-field patterns.