Frequency-dependent attenuation analysis in soils using broadband dielectric spectroscopy and TDR

Our objective is the development of a prognosis system that predicts the soil-dependent GPR performance in landmine and improvised explosive device (IED) contaminated areas. One of the soil properties influencing sensing depth and image resolution of GPR is intrinsic attenuation. We investigated the frequency-dependent electromagnetic properties of a broad range of soil samples. In order to derive the complex dielectric permittivity between 1 MHz and 10 GHz, we applied the coaxial transmission line (CTL) method using two coaxial cells. A model was fitted to the data consisting of a combination of one Debye and one Cole-Cole type relaxation and a constant low-frequency conductivity term. We show that relaxation mechanisms play a crucial role in most natural soils. Attenuation cannot be described by dc-conductivity alone, especially for high-frequency applications. Therefore, a simple conductivity-attenuation relation without relaxations can highly underestimate GPR performance. As an alternative to the CTL technique, we propose to use time-domain reflectometry (TDR) for a quick prediction of high-frequency effective conductivity and GPR performance in the field.