Inversion algorithms and measurement systems for microwave tomography of buried objects

The detection and identification of buried inhomogeneities using electromagnetic waves are of crucial importance for many nondestructive testing applications. The paper deals with two different inversion algorithms for microwave tomography. First, a qualitative algorithm based on diffraction tomography for detecting the buried object, and second, a quantitative algorithm for reconstructing the complex permittivity profile of the object. The backscattered field is measured at different frequencies over a probing line above or in contact with the soil at different receiver locations and for difference positions of a transmitting antenna (multistatic configuration). The two reconstruction algorithms process the backscattered field generated by the buried inhomogeneities and incorporate the incident near-field radiation pattern transmitted in the soil by the broadband antenna. Tomographic reconstructions of buried objects are presented for a situation of practical interest using bow-tie antennas in the frequency band 0.3-1.3 GHz.