A Digital Beamforming Approach for Indoor Passive Sensing

Passive sensing leverages ambient electromagnetic energy to detect target metrics such as distance or motion, reducing the spectral footprint for sensor networks. Recent advancements have shown passive sensing’s ability to sense sub-millimeter scale motions, highlighting the potential for passive sensing to be used in spectrally efficient sensor networks. This paper proposes a passive sensing beamforming technique to achieve direction estimation in passive motion sensors. By performing beamforming in the baseband domain, the direction of a target can be extracted without requiring complex beamforming architectures at the RF front end. A passive beamforming signal model is proposed based on wave propagation models and is simulated to verify its ability to detect angle-of-arrival. The model is then tested experimentally, with results showing the model matches experimental data to a high degree of accuracy and that the beamforming passive radar can accurately determine the position of moving targets to aid in robust sensing.