Passive Non-Cooperative Millimeter-Wave Imaging Using 5G Signals of Opportunity

We present an approach for high-resolution millimeter-wave imaging by capturing non-cooperative communications signals scattered off a scene. Advances in fifth generation (5G) communications are creating an increasingly crowded spectrum at millimeter-wave frequencies, leading to greater interest in spectrum coexistence for functions like sensing and communications. While most research has sought to minimize interference between the two modalities, in this work we exploit a highly dense signal environment where 5G communications transmitters generate a spatio-temporally incoherent signal incident on the scene. We capture the scattered signal in the spatial frequency domain, from which the scene image is reconstructed via inverse Fourier transform. Using four 5G transmitters emitting independent 256-QAM signals, we capture the scattered signals with a 24-element 38 GHz sparse millimeter-wave receiving aperture with no coordination with the transmitters. We demonstrate image reconstruction of multiple targets by implementing this non-cooperative approach.