An Overview of Synthetic-Aperture Image Reconstruction Algorithms for GPR Imaging with Pulse-Echo and Step-Frequency FMCW Systems

The ground-penetrating radar (GPR) systems currently deployed in field applications can be classified into two major types, pulse-echo and step-frequency frequency modulated continuous-wave (FMCW) devices, corresponding to the distinct features of the illumination waveforms. With the addition of synthetic-aperture scans, both versions can be directly applied to high-resolution tomographic imaging. This paper presents the tomographic image reconstruction algorithms for these two operating modalities based on one single framework of backward propagation image formation. In addition to the theoretical analysis and mathematical modeling, this paper presents the algorithm structures for both types of systems as well as results from full-scale field experiments.