Method and device for determining the relative permittivity of a material using a ground-penetrating radar

A method for determining the relative permittivity of a material, comprising the steps:

• step 101:
• acquiring a set of measurements using a ground-penetrating radar provided with NTx transmitting antennas and NRx receiving antennas arranged in a plane parallel to the surface of the material, where NTx and NRx are two positive integers at least equal to two, the set of measurements consisting of impulse responses for each pair consisting of a transmitting antenna and a receiving antenna;
• step 102:
• extracting, from each impulse response, the components relating to multiple paths of the radar signal, in the form of a vector giving the amplitude of the signal as a function of different delay values corresponding to different paths;
• step 103:
• estimating, for each transmitting antenna, a coordinate, in the plane of the radar, of each target associated with a path by finding the coordinate of the receiving antenna that maximizes the impulse response;
• step 104:
• calculating, for a plurality of assumed relative permittivity values of the material, an estimated delay of the radar signal from a hyperbolic curve model defined by the characteristics of the radar and the coordinates of the target associated with a path of the signal;
• step 105:
• finding, in all of the components extracted from the impulse responses, for each pair consisting of a transmitting antenna and a receiving antenna, at least one amplitude associated with a delay closest to the estimated delay calculated in the previous step;
• step 106:
• calculating, for each transmitting antenna, a coefficient of correlation of said amplitudes on all of the receiving antennas;
• iterating steps 104 to 106 for a plurality of relative permittivity values of the material;
• iterating steps 103 to 106 for all of the delay values corresponding to multiple paths of the radar signal in order to obtain NTx correlation matrices giving, for each relative permittivity of the ground value and delay value pair, a correlation coefficient value;
• step 107:
• eliminating the values of the correlation matrices for which the correlation coefficient is less than a predetermined detection threshold;
• step 108:
• filtering the remaining values so as to retain just one vector containing a set of delay values that are all different and an associated relative permittivity of the ground value;
• step 109:
• deducing therefrom, for each layer of the ground, an estimate of its relative permittivity and thickness.