Detecting underground objects by exploiting resonant scatterers with antiresonant antennas

When utilizing an antenna over ground as a near-field probe for detecting underground conducting objects, maximizing the variation in the antenna input impedance due to the buried object is the primary concern. Using the example of a horizontal dipole and a buried cylinder, significant variation in the dipole input impedance is obtained by carefully positioning the antiresonant dipole to excite the dominant cylinder resonance.

I. Introduction

The effectiveness of an antiresonant dipole as a near-field probe for underground object detection has been demonstrated in [1], [2] based on the so-called differential impedance of the antenna. The differential impedance represents the change in the antenna input impedance given the antenna in its geo-environment with and without the presence of the underground object. The dipole is more sensitive to changes in its environment near antiresonance because the feedpoint current is very small at frequencies near antiresonance. In this paper, the inherent sensitivity of an antiresonant antenna is combined with the enhanced antenna-to-scatterer coupling at the dominant resonance of the scatterer to increase the differential impedance. The investigation is carried out via finite difference time-domain (FDTD) simulation.