• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.3
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• pp.132-138
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• 2005

In this paper a DPDT(Double-Pole Double Through) switch with defected ground structure(DGS) is proposed. The equivalent circuit for the proposed switch structure is derived according to based on equivalent circuit of proposed DGS unit structure. The equivalent circuit parameters of DGS unit are extracted by using the circuit analysis method. The on/off operation of the proposed switch is obtained by varying the capacitance of the varactor diode at the defected ground plane. In the case of ON state, the insertion loss of the fabricated DPDT was shown under 1dB. And in OFF state, we found the rejection characteristic over 20dB at the designed frequency 2.45GHz. The experimental results show excellent insertion loss at on state and isolation at off state.

• Journal of the Korean Geotechnical Society
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• v.15 no.5
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• pp.111-124
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• 1999

When deep excavation adjacent to an existing structure is performed, it is very important to minimize damage on the structure through the prediction of ground movement. In this paper, finite element analysis was performed to predict the ground movement, based on the data from site investigation and laboratory tests, when deep excavation close to a buried water tank was carried out in soft clay ground. The movement and stabilities of the soil-cement wall(SCW) and the adjacent structure were checked using the results of the analysis and the field measurement. The comparison between the measured and the predicted ground movements showed the significance of the excavation procedure and lowering of water level in the analytical model. In the future, it is needed to improve the prediction method for better estimation of the ground movement.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.1032-1037
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• 2016

In this paper, the method of isolation enhancement for the mobile phone MIMO antenna of LTE class 40(2300~2400MHz) was studied. Design of MIMO antenna was based on the hybrid antenna that operates both a monopole and an IFA(Inverted F Antenna). A structure for the isolation enhancement which controls induced electric field on the ground plane is located between MIMO antenna, and was not connected with the ground but apart 0.3mm. A MIMO antenna that operates on class 3~40(1710~2400MHz) of LTE service bands and a structure for the isolation enhancement at the class 10 band were designed. VSWR measurement of implemented antenna on the FR4 board showed within 3:1 at entire design bands, and isolation between antennas at the class 40 band was less than -30dB. Isolation was enhanced more than 20dB by the studied structure. ECC(Envelope Correlation Coefficient) for MIMO performance was under 0.1, and antenna average gain and efficiency measured in the anechoic chamber were -4.28~-1.40dBi and 37.32~72.36% respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.6
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• pp.35-41
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• 2011

In order to design effectively the grounding system, it is very important to determine the optimum soil resistivity at the desired location of the connection to earth. This paper deals with the reasonable methods of measuring the soil resistivity where grounding electrodes are buried. The soil resistivity at three test sites with different resistivity of soil were measured as functions of the spacing between the test probes in the Wenner's four-point method and the length of test ground rod in the three-point method. In the case of the three-point method, the length of test ground rod of 2-10[m] in length was appropriate in two-layered soil structure. In the length range of 2-10[m], the results measured by the three-point method using the test ground rod with the length corresponding to the spacing between the test probes of the Wenner's four-point method are in good agreement with the data obtained from the Wenner's four-point method.

• Journal of Electrical Engineering and Technology
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• v.4 no.4
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• pp.531-537
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• 2009

Lightning has a broad frequency spectrum from DC to a few MHz. Consequently, the high frequency performance of grounding systems for protection against lightning should be evaluated, with the distributed parameter circuit model in a uniform soil being used to simulate grounding impedances. This paper proposes a simulation method which applies the distributed parameter circuit model for the frequency-dependent impedance of vertically driven ground rods by considering multi-layered soil structures where ground rods are buried. The Matlab program was used to calculate the frequency-dependent ground impedances for two ground rods of different lengths. As a result, an increase of the length of ground rod is not always followed by a decrease of grounding impedance, at least at a high frequency. The results obtained using the newly proposed simulation method considering multi-layered soil structures are in good agreement with the measured results.

• Proceedings of the Korean Geotechical Society Conference
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• 1995.10a
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• pp.211-216
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• 1995

In recent years, Natm has been successfully applied to difficult ground conditions with the use of soil-perservention methods which promote face stability and restrict excessive ground movement. When the tunnle excavation od made through difficult ground like highly weathered rock, the umbrella arch method is often adopted which pre-reinforceas tunnel crown periphery using a stiff shell-shaped structure. The umbrella arch method was originally developed in Itali, and has recently been confirmed its effectiveness in Korea as well. However, no in depth study on the umbrella arch method has been conducted ans as a result no rational analysis/design method is available at present. Therefore this study was undertaken with the aim of identifying the basic reinforcing mechanism and satablishing both qualitative and quantiative relationships between various design parameters and ground movements.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.523-528
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• 2001

The Capacity Spectrum Method (CSM) was first introduced in the 1970's as rapid evaluation procedure. The procedure compares the capacity of the structure (in the form of a pushover curve) with the demands on the structure (in the form of a response spectrum). The graphical intersection of the two curves approximates the response of the structure. In order to account for nonlinear inelastic behavior of the structural system, effective ductility ratios(μ) are applied to the elastic-linear response spectrum to imitate an inelastic response spectrum. CSM in ATC-40 has deficiencies such as performance point does not converge and the peak deformation of inelastic systems is to be inaccurate when compared against results of nonlinear response history analysis. The purpose of this paper is to investigate the variation of performance points of Capacity Spectrum Method (CSM) are investigated with respect to the different sets of earthquake ground motions. The earthquake sets were used in this study selected by Miranda(1993), Riddell(1991), Seed et al. (1976).

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.2
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• pp.175-182
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• 2002

The cement injection technology on the purpose of ground reinforcement and cut-off has been used in construction sites until now. However, recently it is applied to prevent leakage of underground structure. In this study, applicability of the back side waterproof grouting method was verified through performing field model tests and reviewing case histories. From the results of this study, injection shape of the back side waterproof grouting method was appeared to be root type, and waterproof effect by injection of cement grout material was excellent because grout material infiltrated into boundary between wall of structure and back side ground to be waterproof layer. Components influencing infiltration of injection material are type of soil and degree of compaction. For effective injection, injection pressure has to vary gradually from high pressure to low pessure and small quantity of injection material has to be injected for long times. Also, spacing of injection hole must be designed considering condition of back side ground, injection area, W/C ratio, the number of injection and injection pattern properly.

• Journal of Korean Association for Spatial Structures
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• v.14 no.4
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• pp.89-96
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• 2014

Spatial structures as like dome structure have the different dynamic characteristics from general rahmen structures. Therefore, it is necessary to accurately analyze dynamic characteristics and effectively control of seismic response of spatial structure subjected to multi-supported excitation. In this study, star dome structure that is subjected to multi-supported excitation was used as an example spatial structure. The response of the star dome structure under multiple support excitation are analyzed by means of the pseudo excitation method. Pseudo excitation method shows that the structural response is divided into two parts, ground displacement and structural dynamic response due to ground motion excitation. And the application of passive tuned mass damper(TMD) to seismic response control of star dome structures has been investigated. From this numerical analysis, it is shown that the seismic response of spatial structure under multiple support seismic excitation are different from those of spatial structure under unique excitation. And it is reasonable to install TMD to the dominant points of each mode. And it is found that the passive TMD could effectively reduce the seismic responses of dome structure subjected to multi-supported excitation.

• Journal of the Institute of Convergence Signal Processing
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• v.4 no.1
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• pp.41-48
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• 2003

In this paper, a new equivalent circuit for a defected ground structure(DGS) is proposed and adapted to design of a power amplifier for performance improvement. The DGS equivalent circuit presented in this paper consists of parallel LC resonator and parallel capacitance to describe the fringing fields due to the etched defects on the metallic ground plane, and also is used to optimize the matching circuit of a power amplifier. A previous research has also used a DGS for harmonic rejection and efficiency improvement of a power amplifier(1), however, there was no exact equivalent circuit analysis. In this paper, we suggest a novel design method and show the performance improvement of a class AB power amplifier by using the equivalent circuit of a DGS applied to output matching circuit. The design method presented in this paper can provide very accurate design results to satisfy the optimum load condition and the desirable harmonic rejection, simultaneously. As a design example, we have designed a 20W power amplifier with and without circuit simulation of DGS, and compared the measurement results.