Towards physically-based filtering of the soil surface, antenna and coupling effects from near-field GPR data for improved subsurface imaging

Physically-based filtering of antenna effects in far-field conditions, including antenna-ground interactions, can be performed using intrinsic antenna modeling based on antenna global reflection and transmission coefficients. This has been in particular validated for frequency domain radars for quantitative reconstruction of layered media using full-wave inversion and improved subsurface imaging. In this paper, we further extend the concept to time domain radars for which the source is not separated from the antenna characteristics. Then, we provide insights on the application of the method to near-field conditions. Radar measurements were performed with the antenna at different heights over a perfect electrical conductor (PEC) and on a sandy soil with buried targets. For the PEC measurements, far-field filtering performed very well and also provided relatively good results in near-field conditions, except for the shortest range. Far-field measurements for the sand also provided good results, although the antenna transfer functions had to be corrected to account for the varying time domain radar source (drift). The radar image was not improved for the on-ground radar configuration. Future research will focus on near-field filtering of antenna effects using a recent generalization of the far-field model to near-field conditions.