An analysis technique for buried inhomogeneous dielectric objects in the presence of an air-Earth interface

Complex geological structures are modelled in the presence of an air-Earth interface. A cross-borehole configuration of target, source, and receiver is assumed, with the target itself not restricted as to geometrical cross section or complex permittivity value. Two-dimensional method-of-moment formulations are employed, utilizing cylindrical pulse basis functions and point matching. Scattering from buried dielectric objects is computed near the air-Earth interface for both TE and TM incident fields. A Sommerfeld-Green function is used to represent the effect of the air-Earth interface on the incident fields and the impedance matrix. The TE case is examined for scattering of both the copolarized and cross-polarized electric fields, and several examples are given for a cylindrical target at depths that vary from one to twenty four wavelengths, after which the presence of the air-Earth interface can be neglected. Some experimental results utilizing a 1/40th laboratory scale model and a tunnel-like target are also included for comparison. The technique enables the user to investigate electromagnetic scattering from a variety of complex buried objects whose dimensions are typically in or below the resonance region. The simultaneous relaxation of restrictions on cross section, material properties, and burial depth, together with experimental validation, is not found in the literature to date.<
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