Performances of a Microwave Tomographic Algorithm for GPR Systems Working in Differential Configuration

The imaging capabilities achieved from a ground-penetrating radar (GPR) system based on a contactless differential measurement configuration and from a microwave tomographic approach are investigated. The system is made up of two receiving antennas located at different heights and placed symmetrically with respect to the transmitting antenna. The data, obtained as the difference between the signals measured by the two receivers, are processed by means of a microwave tomographic approach, which is based on a linear model of the electromagnetic scattering and is specifically designed for the differential GPR system. The achievable reconstruction capabilities are theoretically investigated and their dependence on the offset between the receiving antennas is taken into account in order to provide hints about the preferable offset. The theoretical analysis corroborates that, in the case at hand, the reconstructed images are affected by a spatial filtering effect and the retrievable spectral content is reduced by 'hyperbolas of zeroes,' whose occurrence increases with the spatial offset between the two receiving antennas. The effectiveness of the proposed GPR system and of the theoretical analysis is assessed against both synthetic and experimental data.