Wideband Partially-Covered Bowtie Antenna for Ground-Penetrating-Radars

Abstract

Abstract-In this paper, wide band transmitting and receiving antennas; each composed of a bowtie partially covered by an open conducting box; are proposed for ground-penetrating-radar (GPR) system. The inner walls of the conducting box are covered by a lossy coating which is composed of a number of layers with a conductivity profile designed to achieve better characteristics of the bowtie antenna. The Finite-Difference Time-Domain (FDTD) method is applied to simulate the radiating and receiving antennas, the buried target and the wave propagation in the lossy ground soil over the frequency band of operation. The performance of the proposed system is examined as regards the antenna characteristics and the buried target detectability. The impedance and voltage standing wave ratio (VSWR) of the partially covered bowtie antenna are presented over a wide frequency range. The capability of the proposed GPR system to detect targets buried in a ground soil is examined by investigating the change of the coupling between the transmitting and receiving antennas due to the presence of a buried target. The effect of the ground soil on the antenna characteristics is studied for some common types of real soils when the GPR system is placed at different heights above the ground surface.

A Compact Coplanar Broadband Rectangular Slot Antenna With E-Shaped Feeding Structure for GPR Applications

“…A characterization in reflection is generally made to extract the reflection coefficient of each absorbing layer to extract the complex permittivity and the permeability as a function of the frequency. Our model is based on Atteia's simple model [9] which has considered a conductivity profile to reduce sharp reflections at the cavity frontiers. We have previously used this model [16] and observed that S 11 bandwidth remains unchanged as compared to the unshielded case, and also that theoretical and numerical results compare satisfactorily.…”

“…According to previous studies [9,16], a rectangular shield formed of a perfectly conductive box and coated by an inner flat absorbing material has been added. In general, the dielectric characteristics of commercial absorbers are not known for confidential reasons, and approximate models are made.…”

“…By choosing a relative combination of a E-shaped patch, a linear feed line and a rectangular slot, we have designed an antenna structure on a FR4 substrate (h = 1.5 mm) with a very wide operating bandwidth whose nearly half of the spectrum covers frequencies lower than 1 GHz. A partial shield, only opened towards the ground and coated with an inner layered absorbing material, has been added to eliminate undesirable reflections from the upper environment particularly at low frequencies; moreover, in a GPR system, the antenna shielding will allow to reduce the coupling between the transmitting and the receiving units [9].…”

“…Our applications are focused on imaging the subsurface of a large range of civil engineering structures at several depths using a bistatic GPR positioned on or close to the ground surface [8][9][10]. The development of a compact broadband pair of antennas operating in all the frequency band from 0.27 to 3.1 GHz, whose radiation characteristics have been preliminarily studied theoretically in details in different configurations, allows the probing of the subsurface in several frequency sub-bands using a step frequency (SF-GPR) acquisition mode.…”

Complete Dispersion Analysis of Vivaldi Antenna for Ultra Wideband Applications

“…Many kinds of UWB antennas have been introduced such as bow-tie, conical, TEM horn, spiral, fractal, log-periodic and Dragonfly antennas [1][2][3][4][5][6][7]. Owning the suitable design, these antennas show good impedance stability over the large frequency range.…”