DETERMINATION OF GROUND PENETRATING RADAR (GPR) ANTENNA CHARACTERISTICS FOR LABORATORY EXPERIMENT DESIGN

Experiments involving GPR are sensitive to the radiation pattern and corresponding aperture of the antennas. This experiment came to fruition out of a need to acquire radiation patterns for laboratory based GPR data collection including experimental determination of scattering attenuation within periodic and random layered media. The ultimate goal is to develop better tools for separating intrinsic from layering based scattering in layered geologic environments. In this study, a GPR unit will be used to propagate through a periodic media constructed of Styrofoam and medium-density fiberboard pressed together with clamps. For proper interpretation of the amplitudes and corresponding attenuation it is necessary to determine the aperture of the radiated signal to avoid interference due to reflection of waves off the sides of the periodic media. In addition, since amplitudes must be measured to high accuracy, proper characterization of antenna response is necessary for characterization of arbitrary propagation angles through the experimental medium.

To acquire the necessary data we built an apparatus for determination of the antenna radiation pattern. A MALÅ Geoscience Ground Penetrating Radar unit with 1.3 GHz shielded, separable antennas is used to propagate and record waves using both transmission and reflection geometries. To determine the radiation pattern, the apparatus sweeps the receiver through the signal at multiple orientations and distances while keeping the signal and receiver parallel and at identical angles. After controlling for the corresponding response of both the transmitting and receiving antenna we reconstruct the amplitude response of the GPR setup over three dimensions for free space. Future work will include characterizing the effect of antenna coupling with the experimental set-up and finally the characterization of scattering attenuation through layered media.