Sensing and Characterizing the Radio Frequency Field Scattered by a Human Target in an Indoor Environment

In this article, we present a comprehensive exploration of human-induced radio frequency (RF) scattering in indoor environments using a distributed antenna system, supported by the Physical Theory of Diffraction (PTD). Our methodology involves extracting the diffracted field induced by a human target from the forward transmission coefficients of the scattering-parameter (S-parameter) multiport channel matrix. This extraction is performed using two signal processing approaches: the Matrix Pencil Method (MPM) and time-domain gating. To improve efficiency, we further propose a finite rate of innovation (FRI)-based time-domain gating technique that reduces the computational burden while maintaining high resolution, enabling reliable extraction of scattering components. The results are cross-validated with PTD predictions based on a rounded-edge wedge model, which serves as a physically grounded reference for interpreting the spectral content of the scattered field. By comparing the strengths and limitations of each method, we demonstrate how our framework enables the identification of key scattering features, such as shadow radiation and creeping waves, from experimental RF measurements. Furthermore, we leverage the Para-Hermitian Eigenvalue Decomposition (PhEVD) to capture variations in the spatial and spectral structure of the scattered field caused by human presence. This study provides valuable insights into the nuanced interplay between human-induced scattering and RF propagation in indoor environments.