Analysis of the electromagnetic inductive response of a void in a conducting-soil background

A lossless dielectric object situated in a lossy dielectric medium (soil) constitutes a void in a conducting background, which can be detected via an electromagnetic-induction (EMI) sensor operating at appropriate frequencies. The electromagnetic character of this void is dependent on the target and soil properties, as well as on the frequency of operation. We utilize the rigorous method of moments (MoM) and the approximate extended-Born technique to model this three-dimensional (3-D) problem. The modeling algorithms are discussed in detail, with a focus on efficient computation of the dyadic Green's function at the frequencies of interest. The MoM results are used to calibrate the accuracy of the approximate extended-Born solution, over a wide range of operating conditions. Furthermore, the computer simulations are used to perform a detailed phenomenological study.