Extraction of the frequency variation of the complex permittivity using GPR

The objective of this paper is to present an innovative technique for the extraction of the electromagnetic dispersion of civil engineering materials using GPR. This technique is based on a coupling between modified forms of the two-dimensional Fourier transform and a method for the quality factor estimation. It allows identifying the material dispersion phenomena as a variation of the complex permittivity in function of frequency. For each method, an analytical validation is first carried out on simulated propagation signals (generated from one of the Jonscher´s model variants). Second, the radar data collected with the Wide-Angle Reflection and Refraction (WARR) multi-offset geometry were used for experimental validation on limestone and concrete slabs. The complex permittivity obtained by this “inter-method coupling” was compared with that obtained by the semi-destructive measurements using a cylindrical transmission line which is considered as the reference.