Active oolitic sand bars like the modem ones in the Bahamas as well as those in the ancient exhibit a complex internal architecture with a multitude of stacked sedimentary structures. As a result, the internal anatomy of these sand bars is usually too complex to be captured with two-dimensional outcrop and one-dimensional well information. In order to improve fluid flow modeling used in water and hydrocarbon resource management, closely spaced three-dimensional (3-D) data is needed to accurately map sedimentary structures. To improve our understanding of ancient oolitic sand bar anatomy we collected a 3-D 100 MHz Ground-Penetrating Radar (GPR) data cube covering an area of 24x46 m with 7 m penetration depth. A grid spacing of 0.1x0.2 meters is needed to fully exploit the imaging capability of the 100 MHz antennae. The high-resolution 3-D GPR data enable: ○ Volume imaging of oolitic sand bar architecture. ○ Understanding of spatial relationships of sedimentary structures. ○ Reconstruction of depositional environment and assessment of paleocurrent and sandwave migration directions.
{"title":"Reassessment of local paleocurrent directions in the Miami oolitic limestone with 3D ground-penetrating radar","authors":"M. Grasmueck, Ralf J. Weger","doi":"10.1117/12.462244","DOIUrl":"https://doi.org/10.1117/12.462244","url":null,"abstract":"Active oolitic sand bars like the modem ones in the Bahamas as well as those in the ancient exhibit a complex internal architecture with a multitude of stacked sedimentary structures. As a result, the internal anatomy of these sand bars is usually too complex to be captured with two-dimensional outcrop and one-dimensional well information. In order to improve fluid flow modeling used in water and hydrocarbon resource management, closely spaced three-dimensional (3-D) data is needed to accurately map sedimentary structures. To improve our understanding of ancient oolitic sand bar anatomy we collected a 3-D 100 MHz Ground-Penetrating Radar (GPR) data cube covering an area of 24x46 m with 7 m penetration depth. A grid spacing of 0.1x0.2 meters is needed to fully exploit the imaging capability of the 100 MHz antennae. The high-resolution 3-D GPR data enable: ○ Volume imaging of oolitic sand bar architecture. ○ Understanding of spatial relationships of sedimentary structures. ○ Reconstruction of depositional environment and assessment of paleocurrent and sandwave migration directions.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"4758 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129427733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Based on the strengthening example of the historical building, the Shanghai Huifeng Bank Mansion, the methods and efficiency of GPR in non-destructive testing on concrete buildings are discussed in detail. Its successful application into the durability diagnosis of historical buildings is also demonstrated.
{"title":"Case study: GPR testing of a Shanghai historical bank building","authors":"Xiongyao Xie, Yonghui Zhao, Chen Wang","doi":"10.1117/12.462315","DOIUrl":"https://doi.org/10.1117/12.462315","url":null,"abstract":"Based on the strengthening example of the historical building, the Shanghai Huifeng Bank Mansion, the methods and efficiency of GPR in non-destructive testing on concrete buildings are discussed in detail. Its successful application into the durability diagnosis of historical buildings is also demonstrated.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128869808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. Heggy, P. Paillou, F. Demontoux, G. Ruffié, G. Grandjean
Performances of low frequency sounding radars, in term of penetration depth and signal to noise ratio, are mainly function of electric and magnetic losses, volume scattering, and interface roughness. In order to evaluate experimentally the impact of each of those parameters on the future sounding radar missions foreseen for Mars exploration, we conducted series of measurements of the electromagnetic properties of volcanic and sedimentary materials that may be present in the near Martian subsurface layers. Results were used to construct some representatives geoelectrical profiles of the Martian subsurface for the 1-20 MHz frequency range. We considered in particular a simple 3- layered model, which is a primary model to describe terrains where recently observed fluvial-like features raise the possibility that liquid water may exist at shallow depths (100 to 500 meters). We used expected subsurface geophysical conditions such as temperature gradient, rock porosity that may exist for such sites (Clifford, 1993) to construct representative laboratory samples for each layer. We integrated the measured EM characteristics in a geoelectrical model including interface roughness and volume scatterers. We then used the Finite Difference Time Domain (FDTD) algorithm to simulate the radar backscattered echo and evaluate the ability of future sounders to detect the probable presence of ground ice — wateri nterfacei n such a geological configuration.
{"title":"Water detection in the Martian subsurface","authors":"E. Heggy, P. Paillou, F. Demontoux, G. Ruffié, G. Grandjean","doi":"10.1117/12.462293","DOIUrl":"https://doi.org/10.1117/12.462293","url":null,"abstract":"Performances of low frequency sounding radars, in term of penetration depth and signal to noise ratio, are mainly function of electric and magnetic losses, volume scattering, and interface roughness. In order to evaluate experimentally the impact of each of those parameters on the future sounding radar missions foreseen for Mars exploration, we conducted series of measurements of the electromagnetic properties of volcanic and sedimentary materials that may be present in the near Martian subsurface layers. Results were used to construct some representatives geoelectrical profiles of the Martian subsurface for the 1-20 MHz frequency range. We considered in particular a simple 3- layered model, which is a primary model to describe terrains where recently observed fluvial-like features raise the possibility that liquid water may exist at shallow depths (100 to 500 meters). We used expected subsurface geophysical conditions such as temperature gradient, rock porosity that may exist for such sites (Clifford, 1993) to construct representative laboratory samples for each layer. We integrated the measured EM characteristics in a geoelectrical model including interface roughness and volume scatterers. We then used the Finite Difference Time Domain (FDTD) algorithm to simulate the radar backscattered echo and evaluate the ability of future sounders to detect the probable presence of ground ice — wateri nterfacei n such a geological configuration.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"143 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129017930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Moorman, J.-M. Maillol, J. L. Williams, F. S. Walter, W. Glanzman
A detailed GPR survey at the Mahram Bilqis was undertaken to investigate the architectural features buried beneath the desert sands. GPR used in combination with trenching and hand augering for depth verification and material identification, was found to be very effective at mapping the three dimensional location of buried buildings and other subsurface architectural and sedimentary structures. The unique characteristics of the sediment covering the site and the scale of the architectural elements (above and below the surface) presented a number of issues in designing the survey and interpreting the data. The GPR profiles revealed a variety of different structures to a depth of 8 m. The extensive survey and multitude of subsurface features enabled a radar stratigraphic analysis at the site. This was undertaken to classify features according to their geophysical character.
{"title":"Imaging the past: archaeological radar stratigraphic analysis at Mahram Bilqis","authors":"B. Moorman, J.-M. Maillol, J. L. Williams, F. S. Walter, W. Glanzman","doi":"10.1117/12.462200","DOIUrl":"https://doi.org/10.1117/12.462200","url":null,"abstract":"A detailed GPR survey at the Mahram Bilqis was undertaken to investigate the architectural features buried beneath the desert sands. GPR used in combination with trenching and hand augering for depth verification and material identification, was found to be very effective at mapping the three dimensional location of buried buildings and other subsurface architectural and sedimentary structures. The unique characteristics of the sediment covering the site and the scale of the architectural elements (above and below the surface) presented a number of issues in designing the survey and interpreting the data. The GPR profiles revealed a variety of different structures to a depth of 8 m. The extensive survey and multitude of subsurface features enabled a radar stratigraphic analysis at the site. This was undertaken to classify features according to their geophysical character.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115950498","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Two infiltration experiments were conducted to monitor an advancing wetting front at 2.25 m below ground surface with cross-borehole ground penetrating radar (XBGPR). The focus of the experiment was to understand how XBGPR responds to dielectric permittivities that vary on a scale that is smaller than the antenna length. To test this response, a sharp wetting front was formed by applying water evenly over a 5 m by 5 m area at a rate of 5x10-4 cm/s through porous hoses. The center of XBGPR antennae were placed at a depth of 2.25 m in a pair of vertical, PVC lined access tubes located within the irrigated area. The velocity of the first arrival was converted to moisture content using a standard calibration. The measured water content increased linearly with time during the advance of the wetting front. Through comparison with modeled results of flow in unsaturated media, we demonstrate how water contents are "averaged" along the antennae.
{"title":"Measuring the advance of a wetting front using cross-borehole GPR","authors":"D. Rucker, T. Ferré","doi":"10.1117/12.462255","DOIUrl":"https://doi.org/10.1117/12.462255","url":null,"abstract":"Two infiltration experiments were conducted to monitor an advancing wetting front at 2.25 m below ground surface with cross-borehole ground penetrating radar (XBGPR). The focus of the experiment was to understand how XBGPR responds to dielectric permittivities that vary on a scale that is smaller than the antenna length. To test this response, a sharp wetting front was formed by applying water evenly over a 5 m by 5 m area at a rate of 5x10-4 cm/s through porous hoses. The center of XBGPR antennae were placed at a depth of 2.25 m in a pair of vertical, PVC lined access tubes located within the irrigated area. The velocity of the first arrival was converted to moisture content using a standard calibration. The measured water content increased linearly with time during the advance of the wetting front. Through comparison with modeled results of flow in unsaturated media, we demonstrate how water contents are \"averaged\" along the antennae.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131704645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The bowtie antenna provides a solution to the requirements of a broadband non-dispersive antenna for low frequency pulsed ground penetration radar (GPR) applications. This paper reports on a bowtie antenna numerically optimized with respect to bandwidth and radiation performance into the ground over the 10-100 MHz band. Rounding the edges of the bowtie was found to stabilize the antenna performance by reducing the internal angle dependence of the 1St resonant frequency. Half hemisphere radiation was achieved using a nonabsorptive cylindrical cavity placed over the rounded geometry bowtie. Late time ringing due to reflections was minimized by the use of edge termination resistors connected between the cavity wall and the bowtie. The antenna match to the ground was improved using an optimized low permittivity polypropylene slab. This restored the radiation pattern distortion due to the presence of the ground and stabilized the input impedance for fluctuations in ground parameters. This also permitted the antenna to be wheel mounted at various heights above the ground with minimal influence on the antenna performance.
{"title":"Optimized bow-tie antenna for pulsed low-frequency ground-penetrating radar","authors":"M. Birch, K. Palmer","doi":"10.1117/12.462195","DOIUrl":"https://doi.org/10.1117/12.462195","url":null,"abstract":"The bowtie antenna provides a solution to the requirements of a broadband non-dispersive antenna for low frequency pulsed ground penetration radar (GPR) applications. This paper reports on a bowtie antenna numerically optimized with respect to bandwidth and radiation performance into the ground over the 10-100 MHz band. Rounding the edges of the bowtie was found to stabilize the antenna performance by reducing the internal angle dependence of the 1St resonant frequency. Half hemisphere radiation was achieved using a nonabsorptive cylindrical cavity placed over the rounded geometry bowtie. Late time ringing due to reflections was minimized by the use of edge termination resistors connected between the cavity wall and the bowtie. The antenna match to the ground was improved using an optimized low permittivity polypropylene slab. This restored the radiation pattern distortion due to the presence of the ground and stabilized the input impedance for fluctuations in ground parameters. This also permitted the antenna to be wheel mounted at various heights above the ground with minimal influence on the antenna performance.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132232084","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Moulton, D. Wright, Raymond S. Hutton, David V. Smith, J. Abraham
A new high-resolution directional borehole radar-logging tool (DBOR tool) was used to log three wells at the Idaho National Engineering and Environmental Laboratory (INEEL). The radar system uses identical directional cavity-backed monopole transmitting and receiving antennas that can be mechanically rotated while the tool is stationary or moving slowly in a borehole. Faster reconnaissance logging with no antenna rotation was also done to find zones of interest. The microprocessor-controlled motor/encoder in the tool can rotate the antennas azimuthally, to a commanded angle, accurate to a within few degrees. The three logged wells in the unsaturated zone at the INEEL had been cored with good core recovery through most zones. After coring, PVC casing was installed in the wells. The unsaturated zone consists of layered basalt flows that are interbedded with thin layers of coarse-to-fine grained sediments. Several zones were found that show distinctive signatures consistent with fractures in the basalt. These zones may correspond to suspected preferential flow paths. The DBOR data were compared to core, and other borehole log information to help provide better understanding of hydraulic flow and transport in preferential flow paths in the unsaturated zone basalts at the INEEL.
{"title":"Basalt-flow imaging using a high-resolution directional borehole radar","authors":"C. Moulton, D. Wright, Raymond S. Hutton, David V. Smith, J. Abraham","doi":"10.1117/12.462208","DOIUrl":"https://doi.org/10.1117/12.462208","url":null,"abstract":"A new high-resolution directional borehole radar-logging tool (DBOR tool) was used to log three wells at the Idaho National Engineering and Environmental Laboratory (INEEL). The radar system uses identical directional cavity-backed monopole transmitting and receiving antennas that can be mechanically rotated while the tool is stationary or moving slowly in a borehole. Faster reconnaissance logging with no antenna rotation was also done to find zones of interest. The microprocessor-controlled motor/encoder in the tool can rotate the antennas azimuthally, to a commanded angle, accurate to a within few degrees. The three logged wells in the unsaturated zone at the INEEL had been cored with good core recovery through most zones. After coring, PVC casing was installed in the wells. The unsaturated zone consists of layered basalt flows that are interbedded with thin layers of coarse-to-fine grained sediments. Several zones were found that show distinctive signatures consistent with fractures in the basalt. These zones may correspond to suspected preferential flow paths. The DBOR data were compared to core, and other borehole log information to help provide better understanding of hydraulic flow and transport in preferential flow paths in the unsaturated zone basalts at the INEEL.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"133 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131422606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A controlled water production was performed at a water source of Ulaanbaatar city, Mongolia to evaluate the effectiveness of ground penetrating radar for detecting and monitoring dynamic groundwater movements in the subsurface. The groundwater level in Ulaanbaatar city area is between 2m-10m. This relatively shallow depth makes it a suitable target for detection by GPR. Field experiments in Ulaanbaatar were carried out in 2001 with 100 MHz antennae. We measured the groundwater level around a pumping well, then we monitored the change of the level after the pump was stopped. The groundwater level was about 5m. We could detect the groundwater change about 50cm, when the water level in the production well changed by 65cm. If we acquire the data by locating the antenna positions very accurately, we can obtain radar profiles with very high coherency, and we could see the groundwater migration clearly. The CMP was also used in the same site in order to determine the reflection from the groundwater surface. It was found that CMP and velocity analysis give a good information about the depth variation of the groundwater saturation in soil.
{"title":"Groundwater monitoring by GPR in Mongolia","authors":"Q. Lu, Motoyuki Sato","doi":"10.1117/12.462254","DOIUrl":"https://doi.org/10.1117/12.462254","url":null,"abstract":"A controlled water production was performed at a water source of Ulaanbaatar city, Mongolia to evaluate the effectiveness of ground penetrating radar for detecting and monitoring dynamic groundwater movements in the subsurface. The groundwater level in Ulaanbaatar city area is between 2m-10m. This relatively shallow depth makes it a suitable target for detection by GPR. Field experiments in Ulaanbaatar were carried out in 2001 with 100 MHz antennae. We measured the groundwater level around a pumping well, then we monitored the change of the level after the pump was stopped. The groundwater level was about 5m. We could detect the groundwater change about 50cm, when the water level in the production well changed by 65cm. If we acquire the data by locating the antenna positions very accurately, we can obtain radar profiles with very high coherency, and we could see the groundwater migration clearly. The CMP was also used in the same site in order to determine the reflection from the groundwater surface. It was found that CMP and velocity analysis give a good information about the depth variation of the groundwater saturation in soil.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"90 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124740400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Utility mapping using a single-antenna GPR is a timeconsuming operation especially when large areas are to be covered. The data acquisition can be performed much more efficient by using an electronically scanned antenna array. The stepped-frequency 3D GPR that is developed at the Norwegian University of Science and Technology uses a 1 meter wide antenna array that consists of 31 transmit/receive antenna pairs. The main application of the system is utility mapping of streets where the underground consists of a jungle of cables and pipes. The data form the 1 meter wide swath is focused into a 3D image cube using 3D wavenumber migration. By combining several parallel swaths, it is possible to generate underground maps of the whole street at different depths. The radar has successfully been used for mapping of pipes, cables and old tramlines in Trondheim during 2001. The wide bandwidth (100 MHz – 1.6 GHz) gives high enough resolution to map the asphalt thickness and the details of the base layers in addition to the utility lines. In this way, the data from a survey can serve more than one customer. The results from the field tests demonstrate the high user potential of 3D imaging compared to standard 2D GPR profiling.
{"title":"3D utility mapping using electronically scanned antenna array","authors":"E. Eide, J. Hjelmstad","doi":"10.1117/12.462308","DOIUrl":"https://doi.org/10.1117/12.462308","url":null,"abstract":"Utility mapping using a single-antenna GPR is a timeconsuming operation especially when large areas are to be covered. The data acquisition can be performed much more efficient by using an electronically scanned antenna array. The stepped-frequency 3D GPR that is developed at the Norwegian University of Science and Technology uses a 1 meter wide antenna array that consists of 31 transmit/receive antenna pairs. The main application of the system is utility mapping of streets where the underground consists of a jungle of cables and pipes. The data form the 1 meter wide swath is focused into a 3D image cube using 3D wavenumber migration. By combining several parallel swaths, it is possible to generate underground maps of the whole street at different depths. The radar has successfully been used for mapping of pipes, cables and old tramlines in Trondheim during 2001. The wide bandwidth (100 MHz – 1.6 GHz) gives high enough resolution to map the asphalt thickness and the details of the base layers in addition to the utility lines. In this way, the data from a survey can serve more than one customer. The results from the field tests demonstrate the high user potential of 3D imaging compared to standard 2D GPR profiling.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"144 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123576734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper a comprehensive characterization of transient bow-tie antennas for GPR applications is presented. In particular the characteristic impedance of a transient bow-tie antenna above different types of ground, as a function of its flare angle is given. The time-domain reflection coefficient of the transient bow-tie antenna above the ground is derived and also plotted as a function of flare angle. This result shows that there exists an optimal flare angle which gives minimal reflection at the antenna terminal for various ground types. Additionally, here we also investigate the characteristic impedance as a function of antenna elevation above the ground. Moreover, in this paper the subsurface footprints of bow-tie antennas as a function of flare angle for different ground types are shown. This result shows that depending on the target's size, the size of footprint can be adjusted by varying the flare angle in order to reduce clutter from ground surface. The analysis is carried out in the frequency-domain using the mixed-potential integral equation (MPIE) method for problems in multi-layer media, which is solved numerically by the method of moments. The solution in the time domain for transient antennas is obtained using the Fourier transform method and a time window technique to remove open-end reflections.
{"title":"Characterization of transient bow-tie antennas for ground-penetrating radar","authors":"A. A. Lestari, A. Yarovoy, L. Ligthart","doi":"10.1117/12.462193","DOIUrl":"https://doi.org/10.1117/12.462193","url":null,"abstract":"In this paper a comprehensive characterization of transient bow-tie antennas for GPR applications is presented. In particular the characteristic impedance of a transient bow-tie antenna above different types of ground, as a function of its flare angle is given. The time-domain reflection coefficient of the transient bow-tie antenna above the ground is derived and also plotted as a function of flare angle. This result shows that there exists an optimal flare angle which gives minimal reflection at the antenna terminal for various ground types. Additionally, here we also investigate the characteristic impedance as a function of antenna elevation above the ground. Moreover, in this paper the subsurface footprints of bow-tie antennas as a function of flare angle for different ground types are shown. This result shows that depending on the target's size, the size of footprint can be adjusted by varying the flare angle in order to reduce clutter from ground surface. The analysis is carried out in the frequency-domain using the mixed-potential integral equation (MPIE) method for problems in multi-layer media, which is solved numerically by the method of moments. The solution in the time domain for transient antennas is obtained using the Fourier transform method and a time window technique to remove open-end reflections.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"118 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116226651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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