Author ORCID Identifier

https://orcid.org/0000-0001-5129-1205

Date of Award

2026

Document Type

Thesis (Ph.D.)

Department or Program

Engineering Sciences

First Advisor

Dr. Fridon Shubitidze

Second Advisor

Dr. Benjamin Barrowes

Third Advisor

Dr. Ryan Halter

Abstract

Conventional electromagnetic induction (EMI) systems operate within the quasi-static regime, where measurements are dominated by conduction currents and are primarily sensitive to highly conductive targets and bulk soil properties. As a result, these systems exhibit limited sensitivity to low-conductivity and layered media, such as permafrost, composite materials, and minimum-metal landmines, where diagnostically relevant information resides in early-time/high-frequency electromagnetic responses, generally above 100 kHz. This limitation reflects a mismatch between conventional EMI system design and the underlying target physics, restricting the ability of standard EMI approaches to resolve fine-scale non-metallic subsurface structure.

In this thesis, I investigate early-time/high-frequency sensitivity as a unifying design principle for extending EMI sensing beyond the quasi-static regime for geophysical investigations of low-conductivity and layered subsurface targets. I combine electromagnetic modeling, experimental measurements, and signal processing methodologies for both frequency-domain and time-domain EMI systems.

First, I present a novel frequency-domain EMI (FDEMI) system for permafrost detection. Operating in the intermediate-frequency range (~100 kHz–1 MHz), where both conduction and displacement currents contribute to the measured response, the system employs combined geometric and electronic primary-field nulling to enable stable measurement of weak secondary fields at elevated frequencies. Layered-media modeling and field experiments demonstrate sensitivity to low-conductivity soils and permafrost interfaces, with improved spatial resolution relative to conventional EMI approaches.

Second, I extend this framework into the time domain through an early-time electromagnetic induction (ETEMI) system. A custom transmitter and coil configuration enable measurements beginning approximately 3.5 µs after transmitter shutoff. Modeling using the Method of Auxiliary Sources (MAS) and Method of Moments (MoM) demonstrates strong agreement with measured responses from carbon fiber targets and improved sensitivity to low-conductivity and low-metal-content targets, including minimum-metal landmines.

Together, these results establish a unified framework for extending EMI sensing into regimes governed by both conductivity and permittivity.

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