GPR H-plane antenna patterns for a horizontal dipole on a half-space interface

Stanley J. Radzevicius; Jeffrey J. Daniels; Chi-Chih Chen

doi:10.1117/12.383504

27 April 2000 GPR H-plane antenna patterns for a horizontal dipole on a half-space interface

Stanley J. Radzevicius, Jeffrey J. Daniels, Chi-Chih Chen

Proceedings Volume 4084, Eighth International Conference on Ground Penetrating Radar; (2000) https://doi.org/10.1117/12.383504
Event: 8th International Conference on Ground Penetrating Radar, 2000, Gold Coast, Australia

Abstract

GPR dipole antenna patterns can be described by the interference of space and lateral waves. Because this is an interference phenomenon, antenna patterns are a function of frequency, distance, and electrical properties. Traditional far-field criteria based on dipoles in a whole-space are insufficient to describe dipole antennas on a half-space boundary. Whole-space criteria fail because they do not take into account the interference of space and lateral waves. The travel time difference between space and lateral waves increases as the angle of observation from vertical increases, or with increasing distance from the source. The result is increased interference and more abundant lobes with increasing distance and observation angle. Since GPR investigations are limited by attenuation and many environmental and engineering targets of interest are located within a few wavelengths of the antenna, asymptotic solutions do not accurately describe antenna patterns for most GPR applications. The exclusion of lateral waves in geometric optics solutions is another source of error for many GPR applications. Data were measured over a water filled tank to verify FDTD antenna pattern models. Asymptotic solutions predict H-plane peaks at an angular distance equal to the critical angle. Measured and modeled antenna patterns are broader and have peaks located at a larger angular distance, than predicted from asymptotic solutions. The peaks approach and decrease the rate of convergence toward the asymptotic solution with increasing distance from the source, and data modeled over water demonstrate that the peaks still do not converge to the asymptotic solution at a distance of 24 wavelengths. The low directivity of dipole antennas explains why out of the plane reflections are commonly observed in GPR data.

Citation Download Citation

Stanley J. Radzevicius, Jeffrey J. Daniels, and Chi-Chih Chen "GPR H-plane antenna patterns for a horizontal dipole on a half-space interface", Proc. SPIE 4084, Eighth International Conference on Ground Penetrating Radar, (27 April 2000); https://doi.org/10.1117/12.383504

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