Investigations on Radiometric DoA Estimation of Human Body Targets at Ka-Band Using a Space-Division Multiple-Access Approach

In this paper, we present an investigation of a fully passive positioning system based on radiometric measurements. The proposed technology enables passive Direction-of-Arrival (DoA) estimation of human body targets in both indoor and outdoor environments, even under harsh radio conditions. DoA estimation is performed using a likelihood-based method driven by the expected brightness-signal distribution across the radiometer's spatial channels, without requiring the person to wear any active or passive device. Experimental validation in a real-world indoor scenario demonstrates that the proposed single-anchor system enables effective 2D localization, achieving a mean angular error below 3° over distances ranging from 0.5 m to 3 m.