Analysis and theoretical modeling of GPR polarization data

The facts that (1) dipole ground penetrating radar (GPR) antennas radiate linearly polarized waves, (2) dipole receiving antennas are sensitive to the polarization of waves scattered by buried targets, and (3) certain buried targets scatter waves preferentially depending on the polarization of the incident wave mean that polarization is an important consideration in designing GPR data measurement strategy, implementing GPR data processing, and performing GPR data interpretation. In this dissertation, important aspects of GPR polarization phenomena have been analyzed theoretically, numerically, and experimentally.; The first portion of the dissertation presents theory describing polarization phenomena associated with the radiation of electromagnetic waves from dipole antennas and scattering from intrinsic impedance contrasts. Geometrical optics theory is presented to describe the polarization of reflections from objects with dimensions much larger than the incident wavelength. The depolarization of scattering from specular reflectors at low angles of incidence is minimal. However, the fact that the radiated field pattern of a dipole antenna contains crossed-polarized components means that even at low angles of incidence cross-polarized energy may be reflected by targets positioned asymmetrically with respect to the transmitting antenna. The polarization of waves scattered from small-diameter circular cylinders is analyzed using the exact series solution. Small-diameter circular cylinders are significant depolarizers of waves impinging at low angles of incidence. Consequently, polarization-sensitive GPR antenna arrangements (e.g. the crossed-dipole) are useful for detection and identification of targets such as buried pipes.; One chapter in the dissertation describes implementation of the finite-difference time-domain (FDTD) method and compares FDTD generated model data to experimental data to verify the technique can accurately model GPR data. FDTD modeling results are presented in another chapter of the dissertation to provide a quantitative perspective of GPR polarization data. The characteristics of the traces recorded by the modeled monostatic antenna and the distribution of the scattered fields from horizontal interfaces of varying thickness and pipes with differing compositions are analyzed.; Practical benefits of insight into GPR polarization phenomena gained from the research are addressed in the final portion of the dissertation.