Ground Penetrating Radar Antenna Research Articles

Complex image model for ground-penetrating radar antennas

A method of combining the complex image method with the constant Q assumption is derived, which enables the calculation of complex image parameters once for the whole frequency range in the general half-space case. The mixed potential method of moments is then used to model horizontal wire dipoles near a lossy half-space, using pulse-basis functions and point matching. The method is demonstrated by the modeling of two types of wire dipole. A conductive half-wave dipole shows excellent agreement with NEC-S. The current distribution of a 3.4 m resistively loaded dipole across the frequency range 0-512 MHz is also calculated and transformed to the time domain. The result agrees with published measurements. The time required on a workstation was reduced to 4/s per frequency point.

Modeling near‐field GPR in three dimensions using the FDTD method

Complexities associated with the theoretical solution of the near‐field interaction between the fields radiated from dipole antennas placed near a dielectric half‐space and electrical inhomogeneities within the dielectric can be overcome by using numerical techniques. The finite‐difference time‐domain (FDTD) technique implements finite‐difference approximations of Maxwell's equations in a discretized volume that permit accurate computation of the radiated field from a transmitting antenna, propagation through the air‐earth interface, scattering by subsurface targets and reception of the scattered fields by a receiving antenna. In this paper, we demonstrate the implementation of the FDTD technique for accurately modeling near‐field time‐domain ground‐penetrating radar (GPR). This is accomplished by incorporating many of the important GPR parameters directly into the FDTD model. These variables include: the shape of the GPR antenna, feed cables with a fixed characteristic impedance attached to the terminals of the antenna, the height of the antenna above the ground, the electrical properties of the ground, and the electrical properties and geometry of targets buried in the subsurface. FDTD data generated from a 3-D model are compared to experimental antenna impedance data, field pattern data, and measurements of scattering from buried pipes to verify the accuracy of the method.

Measuring flood discharge in unstable stream channels using ground-penetrating radar

Field experiments were conducted to test the ability of ground-penetrating radar (GPR) to measure stream-channel cross sections at high flows without the necessity of placing instruments in the water. Experiments were conducted at four U.S. Geological Survey gaging stations in southwest Washington State. With the GPR antenna suspended above the water surface from a bridge or cableway, traverses were made across stream channels to collect radar profile plots of the streambed. Subsequent measurements of water depth were made using conventional depth-measuring equipment (weight and tape) and were used to calculate radar signal velocities. Other streamflow-parameter data were collected to examine their relation to radar signal velocity and to clarity of streambed definition. These initial tests indicate that GPR is capable of producing a reasonably accurate (±20%) stream-channel profile and discharge far more quickly than conventional stream-gaging procedures, while avoiding the problems and hazards associated with placing instruments in the water.

Ground penetrating radar antennae frequencies and transmitter powers compared for penetration depth, resolution and reflection continuity: H. M. Jol, Geophysical Prospecting, 43(5), 1995, pp 693–709

Twelve ground penetrating radar (GPR) experiments were conducted on the modern, wave-influenced William River delta, on the southern shore of Lake Athabasca in northern Saskatchewan, Canada. The delta is a well-sorted, quartzose-rich, clean, sand-dominated, water-saturated geomorphic feature which provided an ideal site to test GPR. Penetration depths, resolution and continuity of reflections were compared for different antennae frequencies (25, 50, 100, 200 MHz) and transmitter powers (pulser voltage : 400 V, 1000 V). The data show significant variations in vertical resolution from 0.15 m to 0.76 m (200-25 MHz), depth of penetration from 14 m-28 m (200-25 MHz), and continuity of reflections. Increasing the transmitter power from 400 V to 1000 V increases the depth of penetration by 5 to 14% and improves the continuity of reflections with little effect on the resolution.

A Laboratory Appraisal Of Ground·Penetrating Radar Over Water

The work presented here describes an experiment designed to determine the performance and capabilities of ground-penetrating radar (GPR) over water. The main factors that are addressed are: water conductivity and skin depth, accuracy of depth determination, effect of raising the antenna above the water surface plus the radiation pattern and its influence on imaging an inclined submerged interface. This study was undertaken for different frequency GPR antennas which were pulled across the wavetank at Edinburgh University. Two different targets, a metal bar and a plastic plate, were submerged in the tank and the reflections of the electromagnetic signals were recorded. The objective of this work is to clarify the interpretation of GPR images so that field data may be more accurately assessed. Practical applications which could benefit from this work include the investigation of scour around bridge piers and abutments and bathymetric surveys of ponds and lakes.

Ground penetrating radar antennae frequencies and transmitter powers compared for penetration depth, resolution and reflection continuity1

AbstractTwelve ground penetrating radar (GPR) experiments were conducted on the modern, wave‐influenced William River delta, on the Southern shore of Lake Athabasca in northern Saskatchewan, Canada. The delta is a well‐sorted, quartzoserich, clean, sand‐dominated, water‐saturated geomorphic feature which provided an ideal site to test GPR. Penetration depths, resolution and continuity of reflections were compared for different antennae frequencies (25, 50, 100, 200 MHz) and transmitter powers (pulser voltage: 400 V, 1000 V). The data show significant variations in vertical resolution from 0.15 m to 0.76 m (200‐25 MHz), depth of penetration from 14 m‐28 m (200‐25 MHz), and continuity of reflections. Increasing the transmitter power from 400 V to 1000 V increases the depth of penetration by 5 to 14% and improves the continuity of reflections with little effect on the resolution.