Incoherent millimeter-wave imaging using 5G communications signals of opportunity for detection of cracks in building materials

Abstract

We present a new approach to nondestructive evaluation that uses the transmission of noncooperative 5G signals of opportunity and a passive millimeter-wave interferometric imaging system. Interferometric imaging samples scene information in the Fourier domain and reconstructs the image via a two-dimensional Fourier transform, providing an imaging mechanism that does not require mechanical or electronic scanning. To accurately form an image, the incident fields must be spatially and temporally incoherent, a criteria that is satisfied by the transmission of multiple independent 5G communications signals. We demonstrate the ability to image cracks in conducting walls using a sparse interferometric receiver capturing the transmitted 5G signals from two independent transmitters. The 38 GHz interferometric array consists of 24 receiving elements and generates images in real time. We employ deconvolution to remove artifacts resulting from the system point spread function, demonstrating the ability to determine the location of cracks in conducting walls.