Methods and Applications of Near-Field Subsurface Diagnostics

Methods of near-field diagnostics of subsurface inhomogeneities based on the solution of inverse scattering problems in various statements are presented. This diagnostics that provides a subwavelength resolution includes tomography and holography of 3D distributed inhomogeneities as well as the profiling (retrieval of depth profiles) of one-dimensional inhomogeneities. Developed solving algorithms of corresponding inverse scattering problems involve in analysis scattered signals measured by small (with respect to wavelength) antennas in monostatic or bistatic configuration. The depth sensitivity of this diagnostics is achieved using the dependence of the probing field penetration on frequency, antenna altitude, or size of its aperture (multifrequency, pulse, multilevel and multi-aperture methods). In bistatic measurements, we propose here to use also the dependence of the signal formation on parameters of the transmitter-receiver vector (base). These methods can be applied both in electromagnetic and acoustic diagnostics–that demonstrate results of numerical simulations and experimental results obtained for methods based on bistatic measurements with bow-tie antennas and on monostatic measurements with resonant probes.