Beamforming for Unmanned Aerial Vehicle Swarm-Based Distributed Radar Array: Theoretical Analysis and Engineering Demonstration

A distributed radar array (DRA) formed by a swarm of unmanned aerial vehicles (UAVs) is a promising radar system due to its high flexibility and mobility. Beamforming is one of its main functions and there are many challenges to overcome for accomplishing this purpose. In this article, we first establish the beamforming signal model and analyze the effects of the uncertainties in the position, time synchronization, station, and antenna orientation. Then, we construct the objective function considering both the Cramér-Rao lower bound and the peak sidelobe level for the optimal configuration of the UAV swarm as well as realize the fast and efficient solving. Afterward, a phase and gain error compensation strategy is proposed. It includes the localization and time synchronization system design based on high-precision distance measurement and the method of phase and gain errors compensation. The localization and time synchronization system is designed to limit the detrimental effects of the position and time synchronization uncertainties, while the method of phase and gain errors compensation is designed to handle the fixed phase and gain error caused by the position, station, and antenna orientation uncertainties. Finally, the numerical simulation and engineering demonstration validate the feasibility of beamforming for a UAV DRA.