Effects of fractal fluctuations in topographic relief, permittivity and conductivity on ground‐penetrating radar antenna radiation

Abstract

Typical ground‐penetrating radar (GPR) transmitters and receivers are dipole antennas. These antennas have pronounced directivity properties and exhibit strong coupling to interfaces across which there are changes in electric material properties. Antenna coupling to the surface of idealized half‐space models has been the subject of intense research for several decades. In contrast, the behavior of antennas in the vicinity of interfaces with realistic topographic fluctuations and/or subsurface heterogeneities has been largely unexplored. To explore this issue, we simulate the responses of a typical surface GPR antenna system located on a suite of realistic fractal earth models using the finite‐difference time‐domain (FDTD) method. The models are characterized by topographic roughness of the air–soil interface and small‐scale heterogeneous distributions of permittivity and conductivity in the subsurface. Synthetic radiation patterns and input impedance values of the simulated GPR antenna system demonstrate that topographic roughness significantly affects the coupling of the antenna to the ground, whereas heterogeneities in the subsurface predominantly influence the antenna radiation through scattering and absorption along the propagation path.

Soil properties and performance of landmine detection by metal detector and ground-penetrating radar — Soil characterisation and its verification by a field test

“…For GPR, the spatial changes in permittivity generate reflections that can disturb mine signatures and/or create additional responses to the radar. Furthermore, the radiation pattern of antennas is deformed (Lampe and Holliger, 2003;Holliger and Maurer, 2004).…”

“…Dielectric permittivity ε more greatly influences GPR rather than electric conductivity (Lampe and Holliger, 2003;Igel, 2008) and is directly related to the soil water content, as described by the empirical relationship, e.g., Topp's equation (Topp et al, 1980). Dielectric permittivity defines the propagation velocity of the electromagnetic wave as v = 1 = ffiffiffiffiffiffiffi ε μ p , where μ is the magnetic permeability.…”

Enhancing the vertical resolution of surface georadar data

“…The primary reason for the latter is that the antenna-ground coupling for our source estimation procedure is identical to that of a corresponding bi-static surface georadar survey. In this context, it is important to note that depending on the design of the georadar antennas, relatively small changes in the antenna-ground coupling conditions, such as induced by slightly lifting the antennas above the ground, can result in a significant difference of the radiation characteristics and/or the emitted signals (Lampe and Holliger, 2003). Fig.…”

Bayesian frequency-domain blind deconvolution of ground-penetrating radar data

“…However, the unprocessed GPR reflection data provide a blurred and incorrect image of the true subsurface reflectivity structure due to the shape and causal nature of the wavelet embedded in the reflection data (e.g., van Dam and Schlager, 2000). This embedded wavelet has been affected by the source-pulse shape (e.g., Streich and van der Kruk, 2007), the antenna-coupling response (e.g., Lampe and Holliger, 2003) and the earth filter, which introduce amplitude distortions and time delays relative to the earth's reflectivity structure. In this paper, we present a novel blind-deconvolution algorithm that we employ in a new approach to deconvolution for GPR.…”