• Journal of electromagnetic engineering and science
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• 제19권1호
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• pp.64-70
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• 2019

In this study, a compact series-fed center-fed open-stub (SFCFOS) linear array antenna for K-band applications is presented. The antenna is composed of a single-line 10-element linear array. A symmetrical Chebyshev amplitude distribution (CAD) is used to obtain a low sidelobe characteristic against a uniform amplitude distribution (UAD). The amplitude is controlled by varying the width of the microstrip patch elements, and open-ended stubs are arranged next to the last antenna element to use the energy of the radiating signal more effectively. We insert a series-fed stub between two patches and obtain a low mutual coupling for a 4.28-mm center-to-center spacing ($0.7{\lambda}$ at 21 GHz). A prototype of the antenna is fabricated and tested. The overall size of the uniform linear array is $7.04{\times}1.05{\times}0.0563{\lambda}_g^3$ and that of the Chebyshev linear array is $9.92{\times}1.48{\times}0.0793{\lambda}_g^3$. The UAD array yields a ${\mid}S_{11}{\mid}$ < -10 dB bandwidth of 1.33% (20.912-21.192 GHz) and 1.45% (20.89-21.196 GHz) for the CAD. The uniform array design gives a -23 dB return loss, and the Chebyshev array achieves a -30.68 dB return loss at the center frequency with gains of 15.3 dBi and 17 dBi, respectively. The simulated and measured results are in good agreement.

• 한국전자파학회논문지
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• 제30권6호
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• pp.438-444
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• 2019

본 논문에서는 간섭 신호원의 방향을 정확히 탐지 및 식별하기 위해 상호결합특성을 고려한 16소자 배열안테나의 배열 형상 및 개별소자 구조에 대해 연구하였다. 제안된 배열 안테나는 상호결합특성, 능동소자패턴의 편차, 반전력빔폭을 고려하여 개별소자의 접지면간 이격거리를 도출하였다. 개별소자는 마이크로스트립 패치안테나로 구성되며, 광대역 특성 및 안테나의 소형화를 위해 접지면과 연결된 방사체 및 L 모양의 간접 급전 급전부로 구성된다. 제안된 안테나를 사용한 신호탐지 성능 평가 결과 제시된 시나리오 범위 내에서 낮은 RMS(root mean square) error의 성능을 갖는 것을 확인하였다.

• Transactions on Electrical and Electronic Materials
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• 제17권3호
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• pp.150-154
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• 2016

Contact electrodes pose threats like inflammation, metal poisoning, and allergic reaction to the user during long term ECG procedure. Therefore, we present a novel noncontact electrocardiographic electrode designed through microelectromechanical systems (MEMS) process. The proposed ECG electrode consists of small inner and large outer circular copper plates separated by thin insulator. The inner plate enables capacitive transduction of bio-potential variations on a subject’s chest into a voltage that can be processed by a signal processing board, whereas the outer plate shields the inner plate from environmental electromagnetic noise. The electrode lead wires are also coaxially designed to prevent cables from coupling to ground or electronic devices. A prototype ECG electrode has an area of about 2.324 cm², is very flexible and does not require power to operate. The prototype ECG electrode could measure ECG at about 500 um distance from the subject’s chest.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.75-75
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• 2015

Strong interactions between electromagnetic radiation and electrons at metallic interfaces or in metallic nanostructures lead to resonant oscillations called surface plasmon resonance with fascinating properties: light confinement in subwavelength dimensions and enhancement of optical near fields, just to name a few [1,2]. By utilizing the properties enabled by geometry dependent localization of surface plasmons, metal photonics or plasmonics offers a promise of enabling novel photonic components and systems for integrated photonics or sensing applications [3-5]. The versatility of the nanoplasmonic platform is described in this talk on three folds: our findings on an enhanced ultracompact photodetector based on nanoridge plasmonics for photonic integrated circuit applications [3], a colorimetric sensing of miRNA based on a nanoplasmonic core-satellite assembly for label-free and on-chip sensing applications [4], and a controlled fabrication of plasmonic nanostructures on a flexible substrate based on a transfer printing process for ultra-sensitive and noise free flexible bio-sensing applications [5]. For integrated photonics, nanoplasmonics offers interesting opportunities providing the material and dimensional compatibility with ultra-small silicon electronics and the integrative functionality using hybrid photonic and electronic nanostructures. For sensing applications, remarkable changes in scattering colors stemming from a plasmonic coupling effect of gold nanoplasmonic particles have been utilized to demonstrate a detection of microRNAs at the femtomolar level with selectivity. As top-down or bottom-up fabrication of such nanoscale structures is limited to more conventional substrates, we have approached the controlled fabrication of highly ordered nanostructures using a transfer printing of pre-functionalized nanodisks on flexible substrates for more enabling applications of nanoplasmonics.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.320-328
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• 2016

The introduction of renewable energy sources into the AC grid can change and weaken the strength of the grid, which will in turn affect the stability and robustness of the doubly-fed induction generator (DFIG) wind farm. When integrated with weak grids, the DFIG wind turbine with vector power control often suffers from poor performance and robustness, while the DFIG wind turbine with synchronized control provides better stability. This paper investigates the critical short circuit ratios of DFIG wind turbine with vector power control and synchronized control, to analyze the stability boundary of the DFIG wind turbine. Frequency domain methods based on sensitivity and complementary sensitivity of transfer matrix are used to investigate the stability boundary conditions. The critical capacity of DFIG wind farm with conventional vector power control at a certain point of common coupling (PCC) is obtained and is further increased by employing synchronized control properly. The stability boundary is validated by electromagnetic transient simulation of an offshore wind farm connected to a real regional grid.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.223-225
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• 2007

The contact-less inductive power transformer (IPT) uses principle of electromagnetic induction. Generally, there were many methods to improve the transfer performance of traditional transformer. But, though the principle of IPT is similar to that of general transformer, it is impossible to apply the methods because of large air-gap. Consequently, many linear numerical formulas for analysis of performance and design of traditional transformer cannot be used in development of IPT. The concept of the IPT for vehicle like PRT(Personal Rapid Transit) system is suggested and some suggestions for power collector(core & winding) design of IPT to improve power transfer performance arc presented in this paper. The characteristic of power delivery with these novel methods in design is presented by simulation and examination.

• 한국산학기술학회논문지
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• 제11권4호
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• pp.1229-1232
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• 2010

본 논문은 고효율 강압형 적층 압전변압기를 개발하기 위하여 저온소결 세라믹스 개발 및 적층 변압기를 제작하였다. 그리고 회로 요소로써 사용하는 PT는 인버터 설계의 일반적인 접근법을 보여주기 위한 것이다. 또한 압전기 영향의 기술(記述)은 다수의 연구에서 복잡한 방정식과 공식도 쉽게 찾을 수 있다. 특히 압전기 세라믹 EMT가 변화하지 않으며 PT기초 전기소자의 여러 가지 예는 더욱 효과적인 적층변압기의 적용이 가능할 것으로 판단된다.

• 한국초전도ㆍ저온공학회논문지
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• 제19권2호
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• pp.29-32
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• 2017

The use of electronic devices such as mobile phones and tablet PCs has increased of late. However, the power which is supplied through wires has a limitation of the free use of devices and portability. Magnetic-resonance wireless power transfer (WPT) can achieve increased transfer distance and efficiency compared to the existing electromagnetic inductive coupling. A superconducting coil can be applied to increase the efficiency and distance of magnetic-resonance WPT. As superconducting coils have lower resistance than copper coils, they can increase the quality factor (Q-factor) and can overcome the limitations of magnetic-resonance WPT. In this study, copper coils were made from ordinary copper under the same condition as the superconducting coils for a comparison experiment. Superconducting coils use liquid nitrogen to keep the critical temperature. As there is a difference of medium between liquid nitrogen and air, liquid nitrogen was also used in the normal conductor coil to compare the experiment with under the same condition. It was confirmed that superconducting coils have a lower reflection-coefficient($S_{11}$) than the normal conductor coils.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.479-482
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• 2008

In order to more closely examine the vacuum arc phenomena, it is necessary to predict the magnetohydrodynamic (MHD) characteristics by the multidisciplinary numerical modeling, which is coupled with the electromagnetic and hydrodynamic fields, simultaneously. In this study, the thermal-fluid characteristics of high current vacuum arcs were calculated by a commercial multiphysics package, ANSYS, in order to obtain Joule heat, Lorentz force and the interactions with flow variables. We assumed the diffused-mode arc within an AMF vacuum interrupter. It was found with four different currents that the temperature distributions on the anode surface are diffused uniformly without concentration in 7kA for both types (cup and coil-type). But the arc plasma transition and an increase of thermal flux density for increasing the applied current have caused the change of temperature distributions on the anode surface. We should need further studies on the two-way coupling method and radiation model for arc plasmas in order to accomplish the advanced analysis method for multiphysics.

• Composites Research
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• 제17권5호
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• pp.61-67
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• 2004

본 연구에서는 전자파 차폐용 도전성 개스킷 소재로 활용할 수 있는 은입자 충전 실리콘 복합 페이스트에 대한 전기전도성 및 응력-변형율 특성을 분석하였다. 불규칙한 구형의 은(Ag)입자와 상온습기경화형(RTV) 실리콘수지를 도입하여 복합 페이스트의 퍼콜레이션 농도(임계 농도)를 전기전도도 측정 결과로부터 결정하였다. 약 28%의 은입자 함량에서 퍼콜레이션 현상이 발생하였으며, 이 농도에서 급격한 감소를 보이는 은입자/실리콘 복합 페이스트의 체적 비저항, 인장강도 및 연신률의 특성 변화에 관하여 고찰하였다. 또한, 커플링제의 선택적 방법을 통해 퍼콜레이션 농도 이상으로 충전된 복합 페이스트의 응력-변형율 특성을 효과적으로 개선할 수 있음을 제시하여 주었다.