REFLECTION COEFFICIENT OF AN ELECTROMAGNETIC WAVE IN CONDUCTIVE MEDIA

Electromagnetic Waves ◽

Water Contamination ◽

Survey Design ◽

Direct And Inverse Problems ◽

The Difference ◽

Ground Penetrating ◽

Ideal Dielectric

Within the ground penetrating radar bandwidth the medium is considered to be an ideal dielectric, which is not always true. Electromagnetic waves reflection coefficient conductivity dependence showed a significant role of the difference in conductivity in reflection strength. It was confirmed by physical modeling. Conductivity of geological media should be taken into account when solving direct and inverse problems, survey design planning, etc. Ground penetrating radar can be used to solve the problem of mapping of halocline or determine water contamination.

Study Effect of Objects Orientation in the Mediums On GPR Signal Reflections Using FDTD Simulation

European Journal of Engineering Research and Science ◽

10.24018/ejers.2018.3.11.976 ◽

2018 ◽

Vol 3 (11) ◽

pp. 73-77

Author(s):

Aye Mint Mohamed Mostapha ◽

Gamil Alsharahi ◽

Abdellah Driouach

Keyword(s):

Finite Difference ◽

Time Domain ◽

High Frequency ◽

Electromagnetic Waves ◽

Ground Surface ◽

Propagation Path ◽

Fdtd Simulation ◽

Ground Penetrating ◽

Dielectric Objects

Ground penetrating radar (GPR) is a very effective tool for detecting and identifying objects below the ground surface. based on the propagation and reflection of high-frequency electromagnetic waves. The GPR reflection can be affected by many things like the type of objects orientation, their shapes ..ect. The purpose of this paper is to study by simulation the effect of objects orientation in two different mediums (dry and wet sand) on the GPR signal reflection using Reflexw software which is based on a numerical method known as finite difference in time domain (FDTD). The simulations that have been realized included a conductor and dielectric objects. The results obtained have led us to find that the propagation path, the reflection strength and the signal form change with the change of object orientation and nature. To confirm the validity of the results, we compared them with experimental results previously published by researchers under the same conditions.

WISDOM Antenna Pattern in the presence of Rover and Soil

10.5194/egusphere-egu21-14846 ◽

2021 ◽

Author(s):

Wolf-Stefan Benedix ◽

Dirk Plettemeier ◽

Christoph Statz ◽

Yun Lu ◽

Ronny Hahnel ◽

...

Keyword(s):

Pattern Matching ◽

Electromagnetic Waves ◽

Complete System ◽

Near Field ◽

System Model ◽

Soil Types ◽

Broadband Antenna ◽

Shallow Subsurface ◽

The WISDOM ground-penetrating radar aboard the 2022 ESA-Roscosmos Rosalind-Franklin ExoMars Rover will probe the shallow subsurface of Oxia Planum using electromagnetic waves. A dual-polarized broadband antenna assembly transmits the WISDOM signal into the Martian subsurface and receives the return signal. This antenna assembly has been extensively tested and characterized w.r.t. the most significant antenna parameters (gain, pattern, matching). However, during the design phase, these parameters were simulated or measured without the environment, i.e., in the absence of other objects like brackets, rover vehicle, or soil. Some measurements of the rover's influence on the WISDOM data were performed during the instrument's integration.It was shown that the rover structure and close surroundings in the near-field region of the WISDOM antenna assembly have a significant impact on the WISDOM signal and sounding performance. Hence, it is essential to include the simulations' environment, especially with varying surface and underground.With this contribution, we outline the influences of rover and ground on the antenna's pattern and particularly on the footprint. We employ a 3D field solver with a complete system model above different soil types, i.e., subsurface materials with various combinations of permittivity and conductivity.

Evidence for glacial geological controls on the hydrology of Maine (USA) peatlands

Geology ◽

10.1130/g46844.1 ◽

2020 ◽

Vol 48 (8) ◽

pp. 771-776

Author(s):

Xi Chen ◽

Xavier Comas ◽

Andrew Reeve ◽

Lee Slater

Keyword(s):

Peat Soil ◽

Spatial Association ◽

Geochemical Data ◽

Atmospheric Methane ◽

Multiple Sources ◽

Ch4 Production ◽

Geological Factors ◽

Abstract Freshwater pools commonly form eccentric crescent patterns in peatlands, an important atmospheric methane (CH4) source, and show an apparent spatial association with eskers in some deglaciated regions. However, the role of underlying permeable glacial deposits such as eskers in regulating hydrogeology, and perhaps even carbon cycling, in peatlands is rarely considered. In this study, ground-penetrating radar imaging and direct coring confirmed that clustered pools coincide with buried esker crests in contact with peat soil in Caribou Bog and Kanokolus Bog in Maine (USA). Hydraulic head and geochemical data combined with lidar indicate vertical water flow from shallow peat toward the permeable esker crests, suggesting enhanced downward transport of labile organic carbon that presumably accelerates rates of methanogenesis in deep peat. Eskers might therefore serve as proxies for enhanced CH4 production in deep peat, as supported by differences in dissolved CH4 profiles depending on proximity to pools. Geographic data compiled from multiple sources suggest that many peatlands with eccentric pools appear to be located proximal to esker systems in Maine and Fennoscandia. These geological factors may be important, previously unrecognized controls on water and the carbon cycle in peatlands.

Ground‐penetrating radar velocity tomography in heterogeneous and anisotropic media

Geophysics ◽

10.1190/1.1444276 ◽

1997 ◽

Vol 62 (6) ◽

pp. 1758-1773 ◽

Cited By ~ 41

Author(s):

Don W. Vasco ◽

John E. Peterson ◽

Ki Ha Lee

Keyword(s):

Electromagnetic Waves ◽

Numerical Technique ◽

Anisotropic Media ◽

Perturbation Approach ◽

Low Velocity ◽

Weak Anisotropy ◽

Geological Features ◽

Velocity Anomalies ◽

A ray series solution for Maxwell's equations provides an efficient numerical technique for calculating wavefronts and raypaths associated with electromagnetic waves in anisotropic media. Using this methodology and assuming weak anisotropy, we show that a perturbation of the anisotropic structure may be related linearly to a variation in the traveltime of an electromagnetic wave. Thus, it is possible to infer lateral variations in the dielectric permittivity and magnetic permeability matrices. The perturbation approach is used to analyze a series of crosswell ground‐penetrating radar surveys conducted at the Idaho National Engineering Laboratory. Several important geological features are imaged, including a rubble zone at the interface between two basalt flows. Linear low‐velocity anomalies are imaged clearly and are continuous across well pairs.

A Review of Passive and Active Ultra-Wideband Baluns for Use in Ground Penetrating Radar

Remote Sensing ◽

10.3390/rs13101899 ◽

2021 ◽

Vol 13 (10) ◽

pp. 1899

Author(s):

Wouter van Verre ◽

Frank J. W. Podd ◽

Xianyang Gao ◽

David J. Daniels ◽

Anthony J. Peyton

Keyword(s):

Reflection Coefficient ◽

High Speed ◽

Ultra Wideband ◽

Common Mode ◽

Low Frequencies ◽

Essential Components ◽

Phase Balance ◽

Active Balun ◽

Microwave ultra-wideband technology has been widely adopted in instrumentation and measurement systems, including ground-penetrating radar (GPR) sensors. Baluns are essential components in these systems to feed balanced antennas from unbalanced feed cables. Baluns are typically introduced to avoid issues with return signals, asymmetrical radiation patterns and radiation from cables. In GPR systems, these issues can cause poor sensitivity due to a reduction in radiated power, blind spots due to changes in the radiation pattern and additional clutter from common mode radiation. The different balun technologies currently available exhibit a wide variation in performance characteristics such as insertion loss, reflection coefficient and phase balance, as well as physical properties such as size and manufacturability. In this study, the performance of two magnetic transformer baluns, two tapered microstrip baluns and an active balun based on high-speed amplifiers were investigated, all up to frequencies of 6 GHz. A radio frequency current probe was used to measure the common mode currents on the feed cables that occur with poor performing baluns. It was found that commercially available magnetic transformer baluns have the best phase linearity, while also having the highest insertion losses. The active balun design has the best reflection coefficient at low frequencies, while, at high frequencies, its performance is similar to the other baluns tested. It was found that the active balun had the lowest common mode current on the feed cables.

Symmetry between Theoretical and Physical Investigation of Water Contamination Using Amplitude Variation with Offset Analysis of Ground-Penetrating Radar Data

Symmetry ◽

10.3390/sym12060991 ◽

2020 ◽

Vol 12 (6) ◽

pp. 991

Author(s):

Ibrar Iqbal ◽

Gang Tian ◽

Zhejiang Wang ◽

Zahid Masood ◽

Yu Liu ◽

...

Keyword(s):

Aqueous Phase ◽

Water Contamination ◽

Experimental Models ◽

Theoretical Modeling ◽

Avo Analysis ◽

Geophysical Surveys ◽

Phase Liquid ◽

Ground Penetrating ◽

The Impact

We evaluated the symmetry of theoretical and experimental analysis of water contamination such as non-aqueous phase liquid (NAPL) by using amplitude variations with offset analysis (AVO) of ground-penetrating radar (GPR) data. We used both theoretical and experimental approaches for AVO responses of GPR to small distributions of contamination. Theoretical modeling is a tool used to confirm the feasibility of geophysical surveys. Theoretical modeling of NAPL-contaminated sites containing wet sand—both with the water and light non-aqueous phase liquid—was applied by keeping in consideration the GPR AVO analysis in acquisition. Reflectivity was significantly altered with the changes in the contents of water and NAPL during modeling. The wet and dry sands introduced in our model changed two major phenomena: one, the wave pattern—implying a slight phase shift in the wave; and two, an amplitude jump with the dim reflection radar gram observed in the model. Experimental data were collected and analyzed; two observations were recorded during physical data analysis. First, relative permittivity confirmed the presence of NAPL in an experimental tank. Second, reflection patterns with jumps in amplitude and changes in polarity confirmed the theoretical investigation. Our results demonstrate that GPR AVO analysis can be as effective for detection of non-aqueous phase liquid (NAPLs) as it has been used to determine moisture contents in the past. The theoretical and experimental models were in symmetry, and both found a jump in reflection strength. The reflection pattern normally jumped with NAPL-intrusion. From the perspective of water contamination, this study emphasizes the need to take into account the impact of GPR AVO analyses along with the expert’s adaptive capacities.

An automatic approach to delineate the cold–temperate transition surface with ground-penetrating radar on polythermal glaciers

Annals of Glaciology ◽

10.3189/2014aog67a102 ◽

2014 ◽

Vol 55 (67) ◽

pp. 89-96 ◽

Cited By ~ 1

Author(s):

Clemens Schannwell ◽

Tavi Murray ◽

Bernd Kulessa ◽

Alessio Gusmeroli ◽

Albane Saintenoy ◽

...

Keyword(s):

Thermal Structure ◽

Gradual Transition ◽

Signal Power ◽

Automated Method ◽

Automatic Picking ◽

Transition Surface ◽

The Difference ◽

Ground Penetrating ◽

Good Agreement

AbstractGround-penetrating radar has been widely used to map the thermal structure of polythermal glaciers. Hitherto, the cold–temperate transition surface (CTS) in radargrams has been identified by a labour-intensive and subjective manual picking method. We introduce a new automatic approach for picking the CTS that uses the difference in signal power exhibited by the cold and temperate ice layers. We compare our automatically computed CTS depths with manual picks. Our results show very good agreement between the two methods in most areas (r2 > 0.7). RMSEs computed at each trace in two-way travel-time from three test sites range from 14 to 19ns (2.4–3.2 m). The proposed automated method mostly fails in areas showing a rather gradual transition in signal power at the CTS. In some areas, high power originating from non-water sources is misinterpreted by the automatic picking method as ‘temperate ice’.

The Processing Algorithm for Wideband Signals Propagating in Media with Frequency Dispersion

Infocommunications journal ◽

10.36244/icj.2020.3.1 ◽

2020 ◽

Vol 12 (3) ◽

pp. 2-7

Author(s):

Andrei A. Kalshchikov ◽

Vitaly V. Shtykov ◽

Sergey M. Smolskiy

Keyword(s):

Electromagnetic Waves ◽

Flaw Detection ◽

Frequency Dispersion ◽

Debye Model ◽

Processing Algorithm ◽

Chirp Pulse ◽

Wideband Signals ◽

Dispersion Media ◽

The new processing algorithm for wideband signals, which are propagating in frequency dispersion media, is developed in the context of the ground penetrating radar technology. The mathematical substantiation of offered method is presented on the base of linear functional spaces. The method is described for calculation acceleration on the base of the recursive approach. Results of numerical modeling of this method are presented for electromagnetic waves propagating in frequency dispersion media at utilization of chirp pulse signals. The Debye model is used as the model of electrical medium properties. The frequency dispersion of losses in the medium is taken into consideration at modeling. Results of operation modeling of the ground penetrating radar are described. Results of this paper will be useful for the ground penetrating radar technology and the ultrasonic flaw detection.