Modelling time-dependent radio wave scattering from sub-surface ground medium

The interest in non-stationary electromagnetic waves is steadily growing, expanding radar opportunities. Having a wide low-frequency spectrum, the non-stationary radio waves find a use at sounding absorbing environments, in particular, grounds and rocks, and provide large depth of penetration. The problem of transient radio-waves scattering on Earth structures, discussed here, closely adjoins to a problem of interpretation of results of sounding and is one of the major components of work on the increase of efficiency of a subsurface radar. For modeling of non-stationary scattering we use the approach consisting of finding the solution in the frequency domain after a normal impedances method, and its translation in time domain with application of the inverse Fourier transformation. Thus for the given (continuous) law of a humidity change on the depth of a structure on the basis of experimentally received frequency dependences of permittivity and specific conductivity, the appropriate frequency-spatial dependences of these electrical characteristics are formed. A mathematical model, features of construction of the computing algorithm, and basic features of behavior of the transient electromagnetic fields reflected from Earth structures are discussed. Examples of the analysis of obtained results through the inverse-conjugate filtration are summarized, and the limits of its applicability are shown