• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.8
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• pp.93-97
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• 2004

Since powerline for powerline communications (PLC) is designed for supplying electric power using 60 Hz wave, they will have different electrical behaviors for high data rate PLC whose bandwidth is allocated between 1 MHz and 30 MHz. Thus, it is necessary to investigate the different properties in this frequency bandwidth for the high data rate PLC. In this paper, low voltage (220V) powerline impedance for indoor high data rate PLC in between 1 MHz and 30 MHz is measured. For measurement a low voltage coupling unit is made and a vector network analyzer is used. A T-equivalent circuit of the low voltage coupling unit is obtained and then powerline impedance is derived by measuring the reflection coefficient of the total powerline network. With the method proposed, impedance is measured in case of a general korean apartment and its property is analyzed. Measurement shows that the average impedance is about 100Ω.

• Journal of the Korean Institute of Telematics and Electronics
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• v.5 no.4
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• pp.9-19
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• 1968

In this paper, I introduced the theoretical formulas for calcuating the input impedance of a folded dipole antenna which is held in parallel with the conductive supporter. Through the comparision of the above impedance formulas with the imput impedance formulas of a half wave dipole antenna which is parallel to the conductive supporter, it was found that the former can be made in identically same form as the latter, if some conditions are satisfied. The equivalent conditions mentioned above are derived also and the manufacturing of a vertically polarized omni-drectional antenna is apossible by the use of above equivalent conditions, because a half wave dipole antenna in parallel with a conductive supporter is already illustrated to become an omni-directional vertical polarization antenna. Some experimental data are shown together.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.167-177
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• 2002

A test method has been attempted to estimate the soil stiffness by measuring and analyzing dynamic signals of stress waves reflected at the bottom end of the SPT rod contacting a soil deposit. Before conducting a real size testing, a series of parametric studies were conducted in this paper to examine the applicability and the theoretical adequacy of the test method. As a result of these studies, it has been shown that the most significant influence factor affecting the amplitude ratio of the reflected wave to the incident wave at the rod-soil interface was the variation of soil stiffness. Also, the variation of the amplitude ratio was found to be closely related with the variation of impedance ratio of the soil deposit to the SPT rod. As a result, a potential of the test method could be proved to estimate the impedance and the elastic modulus of the soil deposit interfaced with the SPT rod using the test method.

• Structural Engineering and Mechanics
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• v.11 no.5
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• pp.503-518
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• 2001

In this paper, the procedure for deriving an infinite element that is compatible with the quadrilateral Q8 element is first summarized. Enhanced by a self mesh-expansion procedure for generating the impedance matrices of different frequencies for the region extending to infinity, the infinite element is used to simulate the far field of the soil-structure system. The structure considered here is of the box type and the soils are either homogeneous or resting on a bedrock. Using the finite/infinite element approach, a parametric study is conducted to investigate the effect of open and in-filled trenches in reducing the structural vibration caused by a train passing nearby, which is simulated as a harmonic line load. The key parameters that dominate the performance of wave barriers in reducing the structural vibrations are identified. The results presented herein serve as a useful guideline for the design of open and in-filled trenches concerning wave reduction.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.3
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• pp.255-265
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• 2012

This paper presents a 15-GHz multiphase rotary traveling-wave voltage-controlled oscillator (RTW VCO) where a shielded coplanar stripline (CPS) is exploited to provide better shielding protection and lower phase noise at a moderate cost of characteristic impedance and power consumption. Test chips were implemented in a standard 90-nm CMOS process, demonstrating the measured results of 2-GHz frequency tuning range, -11.3-dBm output power, -109.6-dBc/Hz phase noise at 1-MHz offset, and 2-ps RMS clock jitter at 15 GHz. The chip core occupies the area of $0.2mm^2$ and dissipates 12 mW from a single 1.2-V supply.

• Journal of KSNVE
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• v.4 no.3
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• pp.295-305
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• 1994

The reflection coefficient of a material at oblique incidence is measured in a free field. The sound pressure distributions are measured at discrete points on two measurement lines and then decomposed into plane wave components by using spatial Fourier transform. The inciedent and reflected plane wave components are obtained from a set of "decomposition equations" of which uses the plane wave propagation theory. Numerical simulations and experiments have been performed to see the effect of finite size of measurement area. To reduce this effect, a window fuction has been performed to see the effects of finite size of mesurement area. To reduce this effect, a window function has been proposed and its effect on the measurement of sound absorbing material property has been studied as well. The reflection coefficient obtained by this method is compared with those obtained from other methods; 2-microphone method in a duct and an expirical equation of which determines the characteristic impedance .rho.c and propagation constant k of a material from flow resistance information.formation.

• Journal of Biomedical Engineering Research
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• v.26 no.4
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• pp.251-255
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• 2005

When the extracorporeal shock wave lithotriptor is operated, sounds can be heard. Then that might be a question about the location where the sounds come from. For the purpose of investigating the fact, we identify the location of the sounds radiated using one hydrophone. In order to carry out the experiment, it is needed to obtain direct waves from objects. Therefore, we present an experimental method to reduce reflected waves for obtaining direct waves only. The experimental results show the amplitude of waves can be attenuated about 28dB due to a silicon rubber plate of 8.5mm attached at the bottom. This is a quantified result that can expect to obtain the direct waves using the proposed method. Then, we carried out the experiment for the sound source location. From the experimental results, we can undoubtedly present a fact that the sounds are radiated from the objects to be shot due to shock waves.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.2
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• pp.167-174
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• 1996

In this paper, a fault location algorithm is presented, which uses novel signal processing techniques and takes a new paradigm to overcome some drawbacks of the conventional methods. This new method for fault location on electric power transmission lines uses only one-terminal fault signals. The main feature of the method is hat it uses the high frequency components in fault signal and considers the influence of the source network by using a traveling wave propagation characteristics. As a result, we can develop a high speed, good accuracy fault locator.

• Electrical & Electronic Materials
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• v.9 no.1
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• pp.51-58
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• 1996

This report describes thick traveling-wave electrode formation and microwave transmission characteristics of the fabricated electrodes. Effective refractive indices of the microwave in the 5 micron CPW type traveling-wave electrodes is around 2.45 according to the results of time domain S parameter measurements. The bandwidth of the electrodes is about 10 GHz and could be extended to 15 GHz through optimization of the process. The developed process technique that enables plating of micropatterns upto 20 micron can be applied to broadband optical intensity modulators.

• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.434-442
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• 2003

Taking advantage of the probability function, we have analyzed the localization phenomenon of the solution of a propagating function under the condition that the propagation constants are randomly distributed. For example, we have investigated the localization phenomenon of the voltage wave for a transmission line in which the characteristic impedance is randomly distributed. We have confirmed that the localized solution is in existence on the random lossless transmission line. Even in the case that the voltage wave is impulsively excited by the current source, the voltage wave is localized. Because the light wave is seriously affected at the localized position in the lossy transmission line, we have determined that the light wave localization phenomena are generated by multi-reflection.