GeRaF is the first method to use neural implicit learning for near-range 3D geometry reconstruction from radio frequency (RF) signals. Unlike RGB or LiDAR-based methods, RF sensing can see through occlusion but suffers from low resolution and noise due to its lens-less imaging nature. While lenses in RGB imaging constrain sampling to 1D rays, RF signals propagate through the entire space, introducing significant noise and leading to cubic complexity in volumetric rendering. Moreover, RF signals interact with surfaces via specular reflections requiring fundamentally different modeling. To address these challenges, GeRaF (1) introduces filter-based rendering to suppress irrelevant signals, (2) implements a physics-based RF volumetric rendering pipeline, and (3) proposes a novel lens-less sampling and lens-less alpha blending strategy that makes full-space sampling feasible during training. By learning signed distance functions, reflectiveness, and signal power through MLPs and trainable parameters, GeRaF takes the first step towards reconstructing millimeter-level geometry from RF signals in real-world settings.

We present the design, implementation, and evaluation of RFlect, a mmWave imaging system capable of producing around-the-corner high-resolution images in practical environments. RFlect leverages signals reflected off complex surfaces (e.g., poles, concave surfaces, or composition of multiple surfaces) to image objects that are not in the RF line-of-sight. RFlect models the reflections and introduces reconstruction algorithms for different types of surfaces. It also leverages a novel method for precisely mapping the location and geometry of the reflecting surface. We also derive the theoretical resolution and coverage for different reflecting surface geometries. We built a prototype of RFlect and performed extensive evaluations to demonstrate its ability to reconstruct the shape of objects around the corner, with an average Chamfer Distance of 2cm and 3D F-Score of 88.6%.

This paper introduces RFVibe, a system that enables contactless material and object identification through the fusion of millimeter wave wireless signals with acoustic signals. In particular, RFVibe plays an audio sound next to the object that generates micro-vibrations in the object. These micro-vibrations can be captured by shining a millimeter wave radar signal on the object and analyzing the phase of the reflected wireless signal. RFVibe can then extract several features including resonance frequencies and vibration modes, damping time of vibrations, and wireless reflection coefficients. These features are then used to enable more accurate identification, with a step towards generalizing towards different setups and locations. We implement RFVibe using an off-the-shelf millimeter-wave radar and an acoustic speaker. We evaluate it on 23 objects of 7 material types (Metal, Wood, Ceramic, Glass, Plastic, Cardboard, and Foam), obtaining 81.3% accuracy for material classification, a 30% improvement over prior work. RFVibe is able to classify with reasonable accuracy in scenarios that it has not encountered before, including different locations, angles, boundary conditions, and objects.

This paper introduces RFVibe, a system that enables contactless material and object identification through the fusion of millimeter wave wireless signals with acoustic signals. In particular, RFVibe plays an audio sound next to the object that generates micro-vibrations in the object. These micro-vibrations can be captured by shining a millimeter wave radar signal on the object and analyzing the phase of the reflected wireless signal. RFVibe can then extract several features including resonance frequencies and vibration modes, damping time of vibrations, and wireless reflection coefficients. These features are then used to enable more accurate identification, with a step towards generalizing towards different setups and locations. We implement RFVibe using an off-the-shelf millimeter-wave radar and an acoustic speaker. We evaluate it on 23 objects of 7 material types (Metal, Wood, Ceramic, Glass, Plastic, Cardboard, and Foam), obtaining 81.3% accuracy for material classification, a 30% improvement over prior work. RFVibe is able to classify with reasonable accuracy in scenarios that it has not encountered before, including different locations, angles, boundary conditions, and objects.