Coupling Between Highly Conducting and Permeable Metallic Objects in the EMI Frequency Range

Electromagnetic induction (EMI) sensing, from 10's of Hz up to 100's of kHz, is emerging as one of the most promising remote sensing technologies for detection and discrimination of buried metallic objects, particularly unexploded ordinance (UXO). For a single homogenous target it has been shown that the scattered EMI signal strongly depends on an object's geometry and its electromagnetic parameters. Most if not all UXO contain different kinds of metal. Additionally, UXO sites are often highly contaminated with metallic clutter. Methods are currently needed to distinguish dangerous objects, such as UXO, from innocuous clutter. Recently, analysis of broadband EMI responses from multiple objects has demonstrated significant interaction between them. The main goal of the paper is to investigate interaction phenomena between highly conducting and permeable metallic objects in the EMI frequency range. Numerical results are compared with experimental data for canonical geometries (spheres and cylinders). The results indicate when and how interaction affects the EMI responses and provides guidance for use of this understanding for future target discrimination purposes.