AN ANALYSIS TECHNIQUE FOR BURIED INHOMOGENEOUS DIELECTRIC OBJECTS IN THE PRESENCE OF AN AIR-EARTH INTERFACE

The focus of this paper is modeling of complex geological structures i n the presence of an air-earth interface, A cross-borehole configurati on 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, ut ilizing cylindrical pulse basis functions and point matching, Scatteri ng from buried dielectric objects is computed near the air-earth inter face for both TE and TM incident fields. A Sommerfeld-Green function i s used to represent the effect of the air-earth interface on the incid ent fields and the impedance matrix, The TE case is examined for scatt ering of both the copolarized and cross-polarized electric fields, and several examples are given for a cylindrical target at depths that va ry from one to twenty four wavelengths, after which the presence of th e air-earth interface can be neglected. Some experimental results util izing a 1/40th laboratory scale model and a tunnel-like target are als o included for comparison. The technique enables the user to investiga te 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 pro perties, and burial depth, together with experimental validation, is n ot found in the literature to date.