• 대한전자공학회논문지TC
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• 제46권2호
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• pp.114-125
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• 2009

정사각형 기판의 크기가 패치 안테나의 방사 특성에 미치는 영향에 대하여 연구하였다. 기판의 크기가 공진 주파수와 대역폭에 미치는 영향은 매우 작지만 방사 패턴에 미치는 영향은 매우 큼을 볼 수 있었다. 전방방사 이득과 이득이 최대가 되는 각도는 기판의 크기에 따라 거의 주기적으로 변화함을 볼 수 있었다. 전방방사 이득이 최대가 되는 변의 길이와 최소가 되는 변의 길이는 기판의 전기적 두께가 커질수록 작아짐을 볼 수 있었다. 기판의 전기적 두께가 클수록 기판 크기에 따른 전방방사 이득 변화 폭이 큼을 볼 수 있었다. 기판 크기에 따른 방사 패턴의 변화도 기판의 전기적 두께와 매우 밀접한 관계를 가짐을 볼 수 있었다.

• 대한전자공학회논문지TC
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• 제46권6호
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• pp.118-127
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• 2009

정사각형 기판의 크기가 패치 안테나의 방사 특성에 미치는 영향을 연구하기 위하여 마이크로스트립 패치 안테나를 제작하고 측정한 결과를 전산모의한 결과와 비교하였다. 전산모의한 방사 특성 결과와 측정한 방사 특성 결과가 잘 일치함을 볼 수 있었다. 기판의 크기가 패치 안테나의 공진 주파수와 대역폭에 미치는 영향은 작으나 방사패턴에 미치는 영향은 매우 큼을 볼 수 있었다. 기판 두께가 증가할수록 표면파의 발생이 증가하여 기판 크기에 따른 전방 방사 이득 변화 폭, 최대 방사가 일어나는 각도의 변화 폭과 방사패턴의 변화가 크게 발생한다. 기판 두께에 관계없이 기판 크기가 $0.8\;{\lambda}_0$ 일 때 전방방사 이득이 크고 전방방사와 후방방사 이득의 차이도 매우 크다.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1738-1745
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• 2015

Radiation characteristics of a probe-fed rectangular microstrip patch antenna printed on a finite grounded high permittivity substrate are investigated systematically for various square grounded dielectric substrate sizes with several thicknesses and dielectric constants by experiment and full wave simulation. The effect of the substrate size on the radiation characteristics of a rectangular patch antenna is mainly determined by the effective dielectric constant of surface waves on a grounded dielectric substrate. As the effective dielectric constant of surface waves increases, the substrate sizes for the maximum broadside gain and the required onset for a large magnitude of squint angle decrease, while the variations of the broadside gain, the front-to-back ratio, and the magnitude of squint angle versus the substrate size increase due to the increase of the power of the surface wave.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권5호
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• pp.243-248
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• 2001

In this paper, we present theoretical and experimental study on the viscous damping of the on-substrate torsional micromirrors, oscillating near the silicon substrates. In this theoretical study, we develop theoretical models and test structures for the viscous damping of the on-substrate torsional micromirrors. From a finite element analysis, we estimate the theoretical damping coefficients of the torsional micromirrors. From a finite element analysis, we estimate the theoretical damping coefficients of the torsional micromirrors, fabricated by the surface-micromaching process. From the electrostatic test of the fabricated devices, frequency-dependent rotationalvelocity of the micromirrors has been measured at the atmospheric pressure using devices, frequency-dependent rotational velocity of the micromirrors has been measured at the atmospheric pressure using the Mach-Zehnder interferometer system. Experimental damping coefficients have been extracted from the least square fit of the measured rotational velocity within the filter bandwidth of 150 kHz. We have compared the theoretical values and the experimental results on the dynamic performance of the micromirrors. The theoretical analysis overstimates the resonant frequency in the amount of 15%, while underestimating the viscous damping in the factors of 10%.

• 한국재료학회지
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• 제22권9호
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• pp.482-488
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• 2012

To fabricate a precise micro metal mold, the electrochemical etching process has been researched. We investigated the electrochemical etching process numerically and experimentally to determine the etching tendency of the process, focusing on the current density, which is a major parameter of the process. The finite element method, a kind of numerical analysis, was used to determine the current density distribution on the workpiece. Stainless steel(SS304) substrate with various sized square and circular array patterns as an anode and copper(Cu) plate as a cathode were used for the electrochemical experiments. A mixture of $H_2SO_4$, $H_3PO_4$, and DIW was used as an electrolyte. In this paper, comparison of the results from the experiment and the numerical simulation is presented, including the current density distribution and line profile from the simulation, and the etching profile and surface morphology from the experiment. Etching profile and surface morphology were characterized using a 3D-profiler and FE-SEM measurement. From a comparison of the data, it was confirmed that the current density distribution and the line profile of the simulation were similar to the surface morphology and the etching profile of the experiment, respectively. The current density is more concentrated at the vertex of the square pattern and circumference of the circular pattern. And, the depth of the etched area is proportional to the current density.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.81.2-81.2
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• 2012

To fabricate a metal mold for injection molding, hot-embossing and imprinting process, mechanical machining, electro discharge machining (EDM), electrochemical machining (ECM), laser process and wet etching ($FeCl_3$ process) have been widely used. However it is hard to get precise structure with these processes. Electrochemical etching has been also employed to fabricate a micro structure in metal mold. A through mask electrochemical micro machining (TMEMM) is one of the electrochemical etching processes which can obtain finely precise structure. In this process, many parameters such as current density, process time, temperature of electrolyte and distance between electrodes should be controlled. Therefore, it is difficult to predict the result because it has low reliability and reproducibility. To improve it, we investigated this process numerically and experimentally. To search the relation between processing parameters and the results, we used finite element simulation and the commercial finite element method (FEM) software ANSYS was used to analyze the electric field. In this study, it was supposed that the anodic dissolution process is predicted depending on the current density which is one of major parameters with finite element method. In experiment, we used stainless steel (SS304) substrate with various sized square and circular array patterns as an anode and copper (Cu) plate as a cathode. A mixture of $H_2SO_4$, $H_3PO_4$ and DIW was used as an electrolyte. After electrochemical etching process, we compared the results of experiment and simulation. As a result, we got the current distribution in the electrolyte and line profile of current density of the patterns from simulation. And etching profile and surface morphologies were characterized by 3D-profiler(${\mu}$-surf, Nanofocus, Germany) and FE-SEM(S-4800, Hitachi, Japan) measurement. From comparison of these data, it was confirmed that current distribution and line profile of the patterns from simulation are similar to surface morphology and etching profile of the sample from the process, respectively. Then we concluded that current density is more concentrated at the edge of pattern and the depth of etched area is proportional to current density.

• 센서학회지
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• 제8권2호
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• pp.115-123
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• 1999

PSG(800nm)/$Si_3N_4$ (150nm)로 구성된 유전체 membrane 윗면에 heater와 감지전극을 등일면상에 동시에 형성하였다. 제작된 소자의 전체 면적은 $3.78{\times}3.78mm^2$이고, diaphragm의 면적은 $1.5{\times}1.5mm^2$이며, 감지막치 면적은 $0.24{\times}0.24mm^2$였다. 그리고 diaphragm내의 열분포 분석을 유한요소법을 이용하여 수행하였으며, 실제로 제작된 소자의 열분포와 비교하였다. 소비전력은 동작온도 $350^{\circ}C$에서 약 85mW였다. Sn 금속막을 상온과 $232^{\circ}C$의 두 가지 기판온도에서 열증착하였고, 이를 $650^{\circ}C$의 산소분위기에서 3시간 열산화함으로써 $SnO_2$ 감지막을 형성하였다. 그리고 이를 SEM과 XRD로 특성을 분석하였다. 제작된 소자에 대해서 온도 및 습도에 대한 감지막의 영향 및 부탄가스에 대한 반응특성도 조사하였다.