• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.7
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• pp.661-668
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• 2011

Direction estimation of signal of interest has been an important issue in radar and communication system. Generally, DOA(Direction Of Arrival) methods have been researched in the field of signal processing with ideal array sensors. However, there are some problems in array antennas such as the input signal distortions in amplitude and phase, due to the mutual coupling between array elements. In this paper, we propose a new method of DOA estimation in the dipole array antenna by using the method of moment(MoM) to compensate the mutual coupling effects between array antenna elements. Also, the proposed method is applied to the estimation of azimuth(${\phi}$ ) and elevation(${\theta}$) angles using uniformly linear dipole array under noisy environments.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.7
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• pp.800-806
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• 2008

In this paper, a wide-band dipole antenna suitable for use in PCS/WCDMA/WiBro($1.750{\sim}2.39\;GHz$) base station array antenna is presented. The presented antenna is a dipole antenna with pate which has the reflector element and improves the gain flatness. To confirm the wide-band characteristics and the gain flatness of the presented antenna, the experimental antenna is fabricated and its radiation characteristics are measured, compared with calculated results. It is shown that the designed antenna has VSWR less than 1.5, gain over 5 dBi, and gain flatness 0.74 dB in $1.75{\sim}2.39\;GHz$. The measured results show good agreement with the calculated results. From these results, we confirm that the designed antenna can be used as a array element of the wide-band base station array antenna for PCS/WCDMA/WiBro.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.2
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• pp.21-26
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• 2022

In this paper, we investigated the effect of tilting and bending of an 2.45GHz ISM band embroidered dipole array antenna due to the human body movement. The antenna characteristics showed larger variations in tilting on the X-axis than the Y-axis. The antenna gain varied by 0.25[dB] when the antenna tilted by 3.5°. As tilting angle increased the operating frequency(f_o) showed decreasing tendency and the return loss(S₁₁) showed increasing tendency. The antenna characteristics also showed more variation in bending on the X-axis than the Y-axis. As bending the antenna the antenna characteristics affected much more in bending on the X-axis than the Y-axis. The antenna gain varied by 3.73[dB] as the curvature(1/R_rad) increased by 0.04[mm^-1]. As it bended more the operating frequency(f_o) showed decreasing and then increasing tendency and the return loss(S₁₁) showed increasing tendency.

• Journal of the Korean Geophysical Society
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• v.2 no.3
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• pp.217-224
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• 1999

Although faults can be found by geological surveys, the surface traces of faults are not easily discovered by traditional geological surveys due to alluvia. In and around faults and fracture zones, the electrical resistivity appears to be lower than that of the surroundings due to the content of groundwater and clay minerals. Therefore, electrical resistivity surveys are effective to search buried faults and fracture zones. The dipole-dipole array electrical resistivity surveys, which could show the two dimensional subsurface electrical resistivity structure, were carried out in two areas, Yongdang-ri, Woongsang-eup, Yangsan-si, Kyungsangnam-do and Malbang-ri, Woedong-eup, Kyungju-si, Kyungsangpook-do. The one was next to the Dongrae Fault and the other near the Ulsan Fault was close to the region in which debatable quaternary fault traces had been found recently. From each measured data set, the electrical resistivity cross-section was obtained using the inversion program the reliability of which was analyzed using analytic solutions. A low resistivity zone was found in the inverted cross-section from the Yongdang-ri area survey data, and two low resistivity zones were found in that from the Malbang-ri area survey data. They were almost vertical and were 15∼20 m wide. Accounting the shape and the very low resistivity values of those zones (<100 Ωm)in the inverted section, they were interpreted as fracture zones although they should be proven by trenching. The reliability of the interpretation might be improved by adding some more parallel resistivity survey lines and interpreting the results in 3 and/or adding other geophysical survey.

• Journal of the Korean earth science society
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• v.30 no.6
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• pp.699-708
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• 2009

Recently as the interest in the development of domestic ore deposits has increased, we can easily find some studies on exploration geophysics-based ore-deposit survey in literature. Based on the fact that mineralized zone are generally more conductive than surrounding media, electrical resistivity survey among several geophysical surveys has been applied to investigate metallic ore deposits. Most of them are grounded on 2-D survey. However, 2-D inversion may lead to some misinterpretation for 3-D geological structures. In this study, we investigate the feasibility of the 3-D electrical resistivity survey to 3-D vein-type ore deposits. We first simulate 2-D dipole-dipole survey data for survey lines normal to the strike and 3-D pole-pole survey data, and then perform 3-D inversion. For 3-D ore-body structures, we assume a width-varying dyke, a wedge-shaped, and a fault model. The 3-D inversion results are compared to 2-D inversion results. By comparing 3-D inversion results for 2-D dipole-dipole survey data to 3-D inversion results for 3-D pole-pole survey data, we could note that the 2-D dipole-dipole survey data yield better inversion results than the 3-D pole-pole data, which is due to the main characteristic of the pole-pole array. From these results, we are convinced that if we have certain information on the direction of the strike, it would be desirable to apply 2-D dipole-diple survey for the survey lines normal to the strike. However, in most cases, we do not have any information on the direction of the strike, because we already developed the ore deposit with the outcrops and the remaining ore deposits are buried under the surface. In that case, performing 3-D pole-pole electrical resistivity survey would be a reasonable choice to obtain more accurate interpretation on ore body structure in spite of low resolution of pole-pole array.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.191-196
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• 2007

The acoustic array waveforms are simulated in a simple borehole model for both monopole and dipole sources. The model is based on the parameters obtained by the semblance processing of field waveforms collected on the physical models whose physical parameters are known. Both the synthetic and field waveforms are compared to understand the sonic waveform as well as the source wavelet characteristics.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1353-1355
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• 2003

Genetic algorithms (GA) is a well known technique that is capable of handling multiobjective functions and discrete constraints in the process of numerical optimization. Together with the Pareto ranking scheme, more than one possible solution can be obtained despite the imposed constraints and multi-criteria design functions. In view of this unique capability, the design of the log-periodic dipole antenna array (LPDA) using this special feature is proposed in this paper. This method also provides gain, front-back level and S parameter design tradeoff for the LPDA design in broadband application at no extra computational cost.

• The Journal of Engineering Geology
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• v.2 no.1
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• pp.47-57
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• 1992

Geophysical methods applied to water seepage problem in earth-fill embankment attempt to detect and map the estimate of size and depth of the seepage path. Seepage zones generally produce lOW resistivity anomalies due to high saturation of water. Dipole-dipole resistivity surveying technique, which is actually a combined sounding-profiling procedure, was used to delineate the seepage path through this study. In this study, the finite difference methods to solve the electric potential distribution in 2 112 dimension, was adopted as the numerical scheme for the forward problem. Second order Marquart's method, one the iterative damped least square methods, was selected for the automatic inversion. The computer program was implemented in FORTRAN 77 for 1 6-bit personal computer. In this paper, we present a case history which illustrates the application of dipole-dipole resistivity method to the delineation of water flow in earth-fill structures. Also the automatic two-dimensional resistivity inversion was applied to a field data where the interpretive advantages of the program become evident.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1410-1415
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• 2008

This paper proposes an small electronically steerable parasitic array radiator composed of a uniplanar dipole as a feeding element and two dipoles as parasitic elements. The fabricated antenna shows by measurement the $3.3{\sim}4.3\;dB$ gain between $-100{\sim}1000$ azimuth range in the dipole vertical plane and -10 dB return loss within $5.4{\sim}5.9\;GHz$, which includes $5.725{\sim}5.825\;GHz$ UNII band.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.4
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• pp.317-324
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• 2004

Electromagnetically coupled coaxial dipole (ECCD) array antenna with and without short-ended termination is investigated theoretically. The integral equations are derived for the structure by use of the Fourier transform and mode expansion of radial waveguide. The integrals appearing in the integral equations are evaluated along the branch cut instead of real axis for a faster convergent integral. The effects of slots and dipoles, short-ended termination length, and dielectric coating on the radiation characteristics are presented. Radiation pattern of the structure is also investigated. The results of the present method are compared with those of the commercial EM simulator and good agreement is found.