• ETRI Journal
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• 제39권6호
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• pp.866-873
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• 2017

We propose a multilayered-substrate-based power semiconductor discrete device package for a low switching loss and high heat dissipation. To verify the proposed package, cost-effective, low-temperature co-fired ceramic, multilayered substrates are used. A bare die is attached to an embedded cavity of the multilayered substrate. Because the height of the pad on the top plane of the die and the signal line on the substrate are the same, the length of the bond wires can be shortened. A large number of thermal vias with a high thermal conductivity are embedded in the multilayered substrate to increase the heat dissipation rate of the package. The packaged silicon carbide Schottky barrier diode satisfies the reliability testing of a high-temperature storage life and temperature humidity bias. At $175^{\circ}C$, the forward current is 7 A at a forward voltage of 1.13 V, and the reverse leakage current is below 100 lA up to a reverse voltage of 980 V. The measured maximum reverse current ($I_{RM}$), reverse recovery time ($T_{rr}$), and reverse recovery charge ($Q_{rr}$) are 2.4 A, 16.6 ns, and 19.92 nC, respectively, at a reverse voltage of 300 V and di/dt equal to $300A/{\mu}s$.

• ETRI Journal
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• 제38권5호
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• pp.981-987
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• 2016

We present a cost-effective dual polarization quadrature phase-shift coherent receiver module using a silica planar lightwave circuit (PLC) hybrid assembly. Two polarization beam splitters and two $90^{\circ}$ optical hybrids are monolithically integrated in one silica PLC chip with an index contrast of $2%-{\Delta}$. Two four-channel spot-size converter integrated waveguide-photodetector (PD) arrays are bonded on PD carriers for transverse-electric/transverse-magnetic polarization, and butt-coupled to a polished facet of the PLC using a simple chip-to-chip bonding method. Instead of a ceramic sub-mount, a low-cost printed circuit board is applied in the module. A stepped CuW block is used to dissipate the heat generated from trans-impedance amplifiers and to vertically align RF transmission lines. The fabricated coherent receiver shows a 3-dB bandwidth of 26 GHz and a common mode rejection ratio of 16 dB at 22 GHz for a local oscillator optical input. A bit error rate of $8.3{\times}10^{-11}$ is achieved at a 112-Gbps back-to-back transmission with off-line digital signal processing.

• ETRI Journal
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• 제38권2호
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• pp.260-264
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• 2016

We report on highly efficient blue, orange, and white phosphorescent organic light-emitting diodes consisting only two organic layers. Hole transporting 4, 4,' 4"-tris (N-carbazolyl)triphenylamine (TcTa) and electron transporting 2-(diphenylphosphoryl) spirofluorene (SPPO1) are used as an emitting host for orange light-emitting bis(3-benzothiazol-2-yl-9-ethyl-9H-carbazolato) (acetoacetonate) iridium ((btc)2(acac)Ir) and blue light-emitting iridium(III)bis(4,6-difluorophenyl-pyridinato-N,C2') picolinate (FIrpic) dopant, respectively. Combining these two orange and blue light-emitting layers, we successfully demonstrate highly efficient white PHOLEDs while maintaining Commission internationale de l'eclairage coordinates of (x = 0.373, y = 0.443). Accordingly, we achieve a maximum external quantum, current, and power efficiencies of 12.9%, 30.3 cd/A, and 30.0 lm/W without out-coupling enhancement.

• ETRI Journal
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• 제39권2호
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• pp.292-299
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• 2017

We propose pulse-mode dynamic $R_on$ measurement as a method for analyzing the effect of stress on large-scale high-power AlGaN/GaN HFETs. The measurements were carried out under the soft-switching condition (zero-voltage switching) and aimed to minimize the self-heating problem that exists with the conventional hard-switching measurement. The dynamic $R_on$ of the fabricated AlGaN/GaN MIS-HFETs was measured under different stabilization time conditions. To do so, the drain-gate bias is set to zero after applying the off-state stress. As the stabilization time increased from $ 0.1{\mu}s$ to 100 ms, the dynamic $R_on$ decreased from $160\Omega$ to $2\Omega$. This method will be useful in developing high-performance GaN power FETs suitable for use in high-efficiency converter/inverter topology design.

• ETRI Journal
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• 제38권6호
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• pp.1074-1084
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• 2016

This paper presents a transmission method for improving human body communications in terms of spectral efficiency, and the performances of bit-error-rate (BER) and frame synchronization, with a highly simplified structure. Compared to the conventional frequency selective digital transmission supporting IEEE standard 802.15.6 for wireless body area networks, the proposed scheme improves the spectral efficiency from 0.25 bps/Hz to 1 bps/Hz based on the 3-dB bandwidth of the transmit spectral mask, and the signal-to-noise-ratio (SNR) by 0.51 dB at a BER of $10^{-6}$ with an 87.5% reduction in the detection complexity of the length of the Hamming distance computation. The proposed preamble structure using its customized detection algorithm achieves perfect frame synchronization at the SNR of a BER of $10^{-6}$ by applying the proposed pre-processing to compensate for the distortions on the preamble signals due to the band-limit effects by transmit and receive filters.

• ETRI Journal
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• 제41권6호
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• pp.811-819
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• 2019

We propose a substrate with high thermal conductivity, manufactured by the low-temperature co-fired ceramic (LTCC) multilayer circuit process technology, as a new DC/DC converter platform for power electronics applications. We compare the reliability and power conversion efficiency of a converter using the LTCC substrate with the one using a conventional printed circuit board (PCB) substrate, to demonstrate the superior characteristics of the LTCC substrates. The power conversion efficiencies of the LTCC- and PCB-based synchronous buck converters are 95.5% and 94.5%, respectively, while those of nonsynchronous buck converters are 92.5% and 91.3%, respectively, at an output power of 100 W. To verify the reliability of the LTCC-based converter, two types of tests were conducted. Storage temperature tests were conducted at -20 ℃ and 85 ℃ for 100 h each. The variation in efficiency after the tests was less than 0.3%. A working temperature test was conducted for 60 min, and the temperature of the converter was saturated at 58.2 ℃ without a decrease in efficiency. These results demonstrate the applicability of LTCC as a substrate for power conversion systems.

• 한국정보통신학회논문지
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• 제22권5호
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• pp.754-763
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• 2018

선박 ICT융합 장비를 개발하여 선박에 탑재하기 위해서는 형식승인이 필수적으로 이루어져야 하며, 이를 위해서는 환경시험과 기능시험이 요구된다. 환경시험은 대상 장비가 선박 및 해상환경에서 동작하기 위해 요구되는 내구성을 만족하는지 시험하는 것을 의미하며, 기능시험은 대상 장비가 국제표준을 준수하여 고유 기능을 정확하게 수행하는지 시험하는 것을 의미한다. 국내 선박 ICT융합 장비에 대한 환경시험 가능 기관은 227여 곳에 달하는 반면, 기능시험 가능 기관은 전무한 실정이다. 이러한 이유로 현재 선박 ICT융합 장비 기능시험 시설을 구축 중에 있으며, 본 논문에서는 우선적으로 추진 중인 선박 디지털 인터페이스 및 항해통신장비의 기능시험 체계의 개발에 관한 내용을 다룬다. 주요 내용은 대상 장비의 기능시험을 단일 테스트 및 통합 테스트의 두 단계로 수행함으로써 시험 결과의 신뢰성을 향상시키는 것으로, 단일 테스트는 대상 장비의 고유 기능이 정상적으로 동작하는지를 확인하는 것이고, 통합 테스트는 정상적으로 다른 항해통신장비와 조화롭게 동작하는지를 검증하는 것이다. 이를 위해 단일 테스트에 요구되는 부가 연동 장비 등의 필수 기능 요소와 통합 테스트에 요구되는 연계 및 확장 요소를 분석한다.

• 한국컴퓨터산업학회논문지
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• 제3권9호
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• pp.1207-1214
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• 2002

본 연구에서는 ICT(Information ＆ Communication Technology)활용 교수ㆍ학습 지도안을 Web상에서 작성 및 활용이 가능하도록 Web기반 전자지도안 시스템을 개발하여 첫째, 본 시스템만의 ICT 활용 교수ㆍ학습 과정안 형태를 구안하였으며 둘째, 한국형 교육과정과 ICT활용 교수ㆍ학습 과정안의 형태에 맞는 전자 지도안 시스템의 데이터베이스를 설계 및 구축하였으며, 셋째, 손쉽게 전자 지도안을 작성하고 지도안과 ICT 자료들이 효과적으로 연동하도록 시스템을 구현하였다. 마지막으로 구축한 전자 지도안 시스템을 실제 초등학교 현장에 적용하여 지도안 시스템의 효과와 개선점을 분석하였다. 본 전자 지도안 시스템은 수업 현장에서 가장 필요로 하는 ICT자료를 DB화하여 체계적인 지도안을 관리할 수 있다. 또한 지도안과 자료실을 유기적으로 연동시켜 정적인 DB가 동적인 컨텐츠 저장소로 활용할 수 있다. 이 시스템 구축으로 교수학습 지도안의 공유, 활용, 저장성의 극대화를 이룩하였으며 교육 현장에 일반화되어 학교 정보화에 이바지할 것이다.

• 한국전기전자재료학회논문지
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• 제32권2호
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• pp.157-160
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• 2019

P(VDF-TrFE-CFE) (Poly (vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)), which exhibits a high electrostriction of about 7%, can transmit tactile output as vibration or displacement. In this study, we investigated the applicability of P(VDF-TrFE-CFE) to wearable piezoelectric actuators. The P(VDF-TrFE-CFE) layers were deposited through spin-coating, and interspaced with patterned Ag electrodes to fabricate a two-layer $3.5mm{\times}3.5mm$ device. This layered structure was designed and fabricated to increase the output and displacement of the actuator at low driving voltages. In addition, a laser vibrometer and piezoelectric force microscope were used to analyze the device's vibration characteristics over the range of ~200~4,200 Hz. The on-off characteristics were confirmed at a frequency of 40 Hz.

• 한국환경교육학회지:환경교육
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• 제17권1호
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• pp.43-56
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• 2004

The purpose of environmental education is to cultivate democracy citizens suitable for sustainable society. Suitable citizens for sustainable society are fostered person of environmental literacy, environmental sensibility, ecological and synthetic sights of environmental problems, decision making of environmental problems, and environmental responsibility etc. by environmental education. To achieve this purpose of environmental education effectively, it is desirable that produces and utilizes ICT(Information and Communication Technologies) works and methods that can show efficiently special sides(inter-relation, long-term effects etc.) of environmental problems. ICT environmental education materials and methods are raising the interest and participate of teenagers to environmental education because they are accustomed to the Internet in South Korea. Students can easily conversation with the person of similar interests and environment experts through cyber ICT environmental education. The directions of developing ICT teaching materials for environmental education to enforce self-directed learning, cooperation studying etc.