Radar-Based 3-D Spatial Estimation Using Uniquely Identifiable Doppler Tags

3-D spatial information, such as position and orientation estimation, is essential for autonomous systems operating in dynamic and unstructured environments. In this context, radar sensors, known for their robustness to environmental conditions such as dust, fog, and varying lighting, offer promising capabilities for spatial awareness. Therefore, this article presents a radar-based approach for 3-D positioning and orientation estimation using fast-chirp frequency-modulated continuous-wave (FC-FMCW) radar in conjunction with uniquely identifiable Doppler tags. They enable simultaneous identification and high-accuracy range estimation of multiple tagged reference points. The range information is extracted in signal processing while suppressing interference from static objects and other tags. Positioning with four tags is demonstrated as a well-investigated application, while orientation estimation—typically less explored in radar systems—is addressed using a two-tag geometry. Experimental results validate the feasibility and accuracy of the approaches, showing potential for scalable deployment in an industrial context. The findings highlight the capability of radar-tag systems to provide accurate and reliable spatial information and extend their applicability.