High-frequency dual-channel ground-penetrating impulse antenna and method of using same for identifying plastic pipes and rebar in concrete

Abstract

An antenna system for ground-penetrating radar use, comprising first and second co-located antenna element pairs orthogonally oriented with respect to each other. Each of the element pairs includes a transmit element and a receive element. A metallic enclosure (such as a box) shields the element pairs and is open on one side to face a structure to be probed by signals from the transmit elements. The transmit and receive elements are dimensioned, shaped and arranged (a) to achieve low mutual impedance between the elements, (b) to have high sensitivity to reflected signals received from the structure being probed; and (c) to accommodate a desired rise time of a transmit pulse. The transmit elements and receive elements preferably are electrical dipoles but they may also be magnetic dipoles such as slot antennas. When electrical dipoles are employed, they may be formed of elongated diamond-shaped conductive surfaces or be of other appropriate geometries. The transmit and receive elements are positioned within the box and the box dimensioned such that (a) reflections from a top of the box reinforce transmitted signals and (b) the impedance at the feedpoints of the transmit and receive elements is relatively stable as the antenna system is moved over the structure being probed.