• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.10
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• pp.1150-1156
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• 2007

In this paper, two novel subsurface antennas for remote management of underground facilities using PCS and cellular wireless network are proposed. The proposed subsurface antenna is a dual band circular patch which is inserted and molded for the protection of the antenna into a metal such as a manhole cover. The antenna is designed considering the resonant frequency shift of the antenna due to the insertion and molding. The measured return loss and receiving power of the fabricated antenna comparison with a dipole shows that two proposed subsurface antenna can be used for remote management of underground facilities using PCS and cellular systems.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.210-213
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• 2001

In this paper, we analyzed the impedance characteristic of the bow-tie antenna for the broadband operation. The pulsed subsurface radar uses the impulse to collect information for subsurface objects, so the broadband antenna is used to minimize reflections in the feed point for the broadband characteristic of impulse. Therefore, in this paper we analyzed the broadband bow-tie antenna with Ensemble 5.0.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.8
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• pp.1305-1309
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• 2002

Subsurface radar characterize a broadband frequency to collect a information, such as a crack of building, because of using narrow pulse. In this paper, we design a broadband bowtie antenna, using a microstrip, with a FR-4 substrate of ${\varepsilon}_r=4.0$, t=1.6mm. It has a 9.31% bandwidth at s11<-10 dB and s11=-27.45 dB, VSWR=1.089 at 5.78GHz.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.12
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• pp.23-30
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• 1994

In this paper, we present an antenna which can be used for subsurface continuous wave electromagnetic probing. Its input impedance and transmission coefficient of the two port scattering parameters, S$_{21}$, are calculated numerically and the numerical results are compared with measured values from laboratory scale-down experiment. Scale-down experiemtn results using this antenna show that we can detect a metallic pipe, which has 0.8 cm in diameter and buried at a depth of 5.7cm in saline solution, in frequency range from 200 MHz to 1000 MHz.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.281-284
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• 2006

The resistive V dipole (RVD) is a V antenna with both arms loaded with the continuous Wu-King resistive profile. The RVD has many advantages for surface and subsurface probing, such as the ability to radiate a short pulse in a desired direction. The radiated pulse is simply related to the input pulse, e.g., derivative. In addition, it mostly eliminates the multiple reflections between the surface of the ground and the antenna because of its low radar cross section. The drawbacks of the RVD include the high input impedance and the difficulty in implementation. This paper presents ways to improve the accuracy and easiness of the implementation and to improve the low-frequency performance while maintaining the characteristics of the V antenna that are good for probing applications. The implemented antenna is used to form a bistatic radar to scan targets underground, and the result is imaged.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1360-1366
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• 2008

This paper proposes a printed yagi-antenna available at 2.45 GHz, for the remote-management system of the underground equipment. To improve the solidity and waterproof property, the proposed antenna is coated with bakelite. The manufactured antenna is operated at $2.15{\sim}2.52\;GHz$, whose gain measures 10 dBi. These results are a little different from those of the simulated antenna, but the trend is totally similar. Developed antenna is expected to be useful in the underground facility.

• Journal of the Korean Geophysical Society
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• v.7 no.3
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• pp.161-170
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• 2004

Examples of GPR survey results at a variety of archaeological sites are presented. Several new analyses which include static corrections for the tilt of the GPR antenna are shown for imaging of burial mounds with significant topography. Example archaeological site plans developed from GPR remote sensing of Roman and Japanese sites are given. The first completely automated GPR survey, using only Global Positioning Satellite navigation to create 3D data volumes, is employed for a site in Louisiana to detect lost graves of the Choctaw Indian Tribe.

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.2 s.17
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• pp.1-8
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• 2005

Microwave tomographic imaging technology using a bi-focusing operator has been developed in order to detect the internal voids/objects inside concrete structures. The imaging system consists of several cylindrical or planar array antennas for transmitting and receiving signals, and a numerical focusing operator is applied to the external signals both in transmitting and in receiving fields. In this study, the authors developed 3-dimensional (3D) electromagnetic (EM) imaging technology to detect such damage and to identify exact location of steel rebars or dowel. The authors have developed sub-surface two-dimensional (2D) imaging technique using tomographic antenna array in previous works. In this study, extending the earlier analytical and experimental works on 2D image reconstruction, a 3D microwave imaging system using tomographic antenna way was developed, and multi-frequency technique was applied to improve quality of the reconstructed image and to reduce background noises. Numerical simulation demonstrated that a sub-surface image can be successfully reconstructed by using the proposed tomographic imaging technology. For the experimental verification, a prototype antenna array was fabricated and tested on a concrete specimen.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.11
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• pp.1307-1314
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• 2012

To reduce the effects of clutters with subsurface inhomogenities in ground-penetrating radar(GPR) images, an eigenimage based signal-processing technique is presented. If the conventional eigenimage filtering technique is applied to B-scan images of a GPR survey, relatively homogeneous clutters such as antenna ringing, direct coupling between transmitting and receiving antennas, and soil-surface reflection, can be removed sufficiently. However, since random clutters of subsurface inhomogenities still remain in the images, target signals are distorted and obscured by the clutters. According to a comparison of the eigenimage filtering results, there is different coherency between subsurface clutters and target signals. To reinforce the pixels with high coherency and reduce the pixels with low coherency, the pixel-by-pixel geometric-mean process after the eigenimage filtering is proposed here. For the validity of the proposed approach, GPR survey for detection of a metal target in a randomly inhomogeneous soil is numerically simulated by using a random media generation technique and the finite-difference time-domain(FDTD) method. And the proposed signal processing is applied to the B-scan data of the GPR survey. We show that the proposed approach provides sufficient enhancement of target signals as well as remarkable reduction of subsurface inhomogeneous clutters in comparison with the conventional eigenimage filtering.

• Geophysics and Geophysical Exploration
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• v.9 no.4
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• pp.279-290
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• 2006

The borehole radar methods used to tunnel detection are mainly classified into borehole radar reflection, directional antenna, crosshole scanning, and radar tomography methods. In this study, we have investigated the feasibility and limitation of each method to tunnel detection through case studies. In the borehole radar reflection data, there were much more clear diffraction signals of the upper wings than lower wings of the hyperbolas reflected from the tunnel, and their upper and lower wings were spreaded out to more than 10m higher and lower traces from the peaks of the hyperbolas. As the ratio of borehole diameter to antenna length increases, the ringing gets stronger on the data due to the increase in the impedance mismatching between antennas and water in the boreholes. It is also found that the reflection signals from the tunnel could be enhanced using the optimal offset distance between transmitter and receiver antennas. Nevertheless, the borehole radar reflection data could not provide directional information of the reflectors in the subsurface. Direction finding antenna system had a advantage to take a three dimensional location of a tunnel with only one borehole survey even though the cost is still very high and it required very high expertise. The data from crosshole scanning could be a good indicator for tunnel detection and it could give more reliable result when the borehole radar reflection survey is carried out together. The images of the subsurface also can be reconstructed using travel time tomography which could provide the physical property of the medium and would be effective for imaging the underground structure such as tunnels. Based on the results described above, we suggest a cost-effective field procedure for detection of a tunnel using borehole radar techniques; borehole radar reflection survey using dipole antenna can firstly be applied to pick up anomalous regions within the borehole, and crosshole scanning or reflection survey using directional antenna can then be applied only to the anomalous regions to detect the tunnel.