Accurate 3-D Motion Tracking Based on Radar Distributed Network

This article examines the feasibility of measuring the three-dimensional (3D) displacement of moving targets using a distributed network of three 24 GHz Doppler radars positioned along orthogonal axes. Though radar sensors offer advantages over optical sensors in terms of cost and privacy, conventional phase-based estimation fails during stationary periods or with multi-component targets. To address these issues, this work proposes a displacement detection method based on an ad-hoc experimental setup and the micro-Doppler signature. A curve extraction algorithm isolates the different body parts, which are then integrated over time to determine displacement. The proposed method is validated through both simulation and measurements and supported by a stereophotogrammetric system as ground truth. The system's effectiveness was further demonstrated through a proof-of-concept human walking trial, proving that micro-Doppler analysis can overcome the limitations of classical phase-based methods in biomechanical applications.