• Journal of electromagnetic engineering and science
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• v.7 no.4
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• pp.190-194
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• 2007

In this paper, a cross-coupled microstrip combline bandpass filter using stepped-impedance resonators(SIRs) is proposed. In order to improve the selectivity as well as the insertion loss, the SIR configuration is used. The cross coupling is also introduced to enhance the selectivity. The improvement of the insertion loss is demonstrated not only by deriving the quality factor of the SIR but through the measured performances. Both the proposed and the conventional combline bandpass filter with 5 % of fractional bandwidth at 2 GHz were fabricated and tested. Compared to the conventional combline bandpass filter, the proposed one exhibits the improved selectivity as well as the lower insertion loss characteristics.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1348-1349
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• 2008

Grounding impedance depends on the frequency of current flowing into a grounding system. Especially, the lightning gives a broad frequency spectrum from low frequency up to 1 MHz. So the grounding impedance related to high frequency current like lightning should be measured with high frequency source. In this paper, we described the grounding impedances of deeply-driven ground rods of 10 $\sim$ 48 m long with respect to the frequency of injected currents. For the experiments, we used the wideband power amplifier which can produce sinusoidal voltages with the frequency ranges of DC $\sim$ 250 MHz. As a result, the longer the ground rod is, the lower the ground resistance is. However the grounding impedance of deeply-driven ground rod in the range of higher frequency is significantly increased. As a consequence, it is important to evaluate the high frequency performance of grounding systems for lightning protection.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.7
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• pp.1181-1186
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• 2008

A impedance model simulating the electrical characteristics of the External Electrode fluorescent lamp operated at high frequency is proposed. The model is constructed from a two parameter equation which is derived based on a set of two measurements. This is a readily constructed and computer simulator oriented model which is suitable for a preliminary design of electronic ballasts. Simulated and experimental results are used to verify the analytical discussions, and moreover, an electronic ballast design example using the proposed model is presented to further demonstrate its application.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.2
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• pp.149-157
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• 2003

The purpose of this paper is to quantitatively investigate aging state of epoxy coating on containment structure at nuclear power plant. In order to evaluate an physical bonding of the epoxy coating, adhesion test was performed on a degraded epoxy coating on concrete specimens fabricated by accelerated aging experiment. In addition, impedance data by ultrasonic test were measured to compare with adhesion data. From almost 50 % of the specimens, aging phenomena of epoxy coating such as pin hole, blistering was discovered. To improve reliability on quality degradation of epoxy, co-relation between two kinds of different data was analyzed. By tracing co-related these data, it was possible to figure out physical state of as-built epoxy coating. The possibility to develop new methodology of time - dependent aging state on epoxy coating was found and discussed.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.1
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• pp.22-24
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• 2012

Depending on the status of the engine oil, the dielectric constant is changed. Dielectric constant of oil is related to the characteristic impedance of the probe and the characteristic impedance of the probe determines the reflected signal. In this paper, we derive an equivalent circuit of the probe and using the dielectric constant obtained by measuring the capacitance, the theoretical reflection coefficient of the probe was calculated. In the results, if the engine oil is deteriorated, we can see that the reflection coefficient is increased.

• 전기의세계
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• v.21 no.1
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• pp.7-12
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• 1972

General steady state equivalent circuits are derived for the family of single phase motor having two windings with non-quadrature. First, the fundamental voltage equations of motor are derived by Faraday-Krichhoff's low in the fiew of the flux distribution in the modified motor with Kron primitive machine. Those equations are arranged in to f-b equations by transformation matrix. To using the above equations for circuit; 1) The concept of current-source was much help to sove the realtions between matrix impedance equation and circuit analysis 2) The simplification of the circuit to the mutual impedance matrix elements is easy to considerations of motor characteristics in the case of inserted external auxiliary winding impedance. Finally, this equivalent circuit showing as a single phase induction motor with quadrature winding is described by each conditions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.4
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• pp.649-656
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• 2000

In this paper, a closed exact from and its approximation of the characteristic impedance of a lossy coaxial line with a thick outer conductor are proposed. It is also shown for 3.5mm reference air line that the proposed approximation is accurate over the entire operating frequency range of the line.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.6
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• pp.295-301
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• 2001

In this paper, an impedance control using a serial chain of spring-damper system is proposed for a vehicle platoon. For safety of the vehicle platoon, it is required to regulated the distance between each vehicle at a preassigned value even in case of vehicle model error, or moise in the measurement signal. Since the spring-damper system is physically stable and widely used to represent the interaction with the uncertain environments, it is appropriate to the longitudinal control of the vehicle platoon. By considering the nonholonomic characteristics of the vehicle motion, the lateral control and the longitudinal control of the vehicle paltoon are unified in the proposed algorithm. Computer simulation is carried out to verify the robustness against the uncertainties such as the vehicle model error and the measurement noise.

• Journal of the Korean Ceramic Society
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• v.31 no.9
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• pp.1012-1220
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• 1994

BaTiO3 ceramics doped with 0.1 to 4.0 mol% Nb2O5 were prepared by conventional solid stage sintering process, so as to investigate the effect of the amount of Nb2O5 on the dielectric properties and complex impedance patterns of barium titanates. From the measurement of capacitance, we found that the dielectric constant of BaTiO3 samples with 1 mol% or more Nb2O5 remained approximately constant around room temperature with values higher than 2500. In this paper, the effect of impurity content as well as temperature on complex impedance patterns was discussed in detail. In particular, the grain and grain boundary behavior of samples which showed PTCR characteristics was discussed in terms of measuring temperature.

• Journal of the Korean Ceramic Society
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• v.33 no.1
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• pp.35-40
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• 1996

The influence of grain boundary on the electrical properties of WO3-doped SrTiO3 ceramics has been investi-gated. From the result resistivity and capacitance of grains and boundaries were obtained by employing impedance spectrocopy. And the temperature dependance of capacitance of WO3-doped SrTiO3. was influenced directly by the variation of grain boundary capacitance. It was also found by impedance spectroscopy that the dispersion frequency characteristics showed discernibly that the resistivity of the specimen varied with WO3 content.