• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.21 no.1
• /
• pp.35-41
• /
• 2007

Recently, there are increasing social needs for stable supply of electric power and securing high quality of information and communication services. In this work, to propose the effective protection countermeasures of information-oriented equipments against lightning surges, the protection effects of surge protective devices(SPDs) were experimentally investigated using actual-sized test circuits in various installation conditions. As a result, it was found that the protection effect of SPDs is quite different depending on the factors, such as the grounding system of power source, numbers of branch circuits, wiring method of grounding leads, and etc. In case of installing SPDs for information-oriented equipments, including all electric power lines and communication lines, the common grounding should be the most effective. Wiring method containing grounding leads with power lines in metal conduit is suitable to improve the surge cutoff performance of SPDs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.9
• /
• pp.985-991
• /
• 2008

This paper presents a novel balanced mixer receiver front-end design based on a metamaterial structure applicable to differential-/common-mode excitation. This metamaterial structure functions as a leaky-wave antenna and provides in-trinsic common-mode suppression. Low LO leakage and high RF to LO isolation are achieved without additional filters for LO and RF paths. The metamaterial is based on a unit-cell which under a differential-mode excitation behaves like a composite right/left-handed(CRLH) metamaterial. In contrast, the metamaterial unit-cell is below cut-off under a common-mode excitation. Experimental results are used to verify the proposed metamaterial's differential-/common-mode characteristics. The metamaterial is integrated with a balanced mixer design resulting in an operation frequency range of $1.96{\sim}2.40$ GHz with an optimum mixer conversion loss of 21.1 dB at 2,4 GHz.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38A no.1
• /
• pp.79-87
• /
• 2013

A new modulation technique - correlative encoded FSK (CEFSK) - for use in power and bandwidth limited digital communication system is proposed. CEFSK is free of ISI and generates output signals which have a smooth and continuous phase transition and a reduced envelope fluctuation by keeping correlation between amplitude and phases of two subsequent symbols. In comparison to conventional one-bit differential detected (1DD) GFSK, the performance of the 1DD-CEFSK in a non-linearly amplified (NLA) channel impaired by additive white Gaussian noise (AWGN), ISI and IM, is analyzed via computer simulation. The simulation result shows that, in an NLA single-channel, 1DD-CEFSK provides a signal-to-noise ratio (SNR) advantage of up to 1.2dB and 0.8dB at BER of $1{\times}10^{-4}$ when input back-off (IBO) of HPA is -1.0dB and -3.0dB, respectively. For the same channel environment with multi-channel, 1DD-CEFSK outperforms 1DD-GFSK by 1.1dB in SNR, regardless of the value of IBO.

• Journal of Advanced Marine Engineering and Technology
• /
• v.34 no.2
• /
• pp.332-338
• /
• 2010

Annually, electrical fires caused by arcing phenomena in power system rapidly increase as the use of more electric appliances, but there is no established method for the prevention of the accidents. With this background, this paper dealt with the experimental results on a series arc detection technique and a device for air conditioners. Series arcing phenomena that is generated in incomplete connection of air conditioners was simulated, and the frequency spectrum was analyzed. The Fast Fourier Transform (FFT) of the arc pulse showed that the dominant frequency components exist in ranges of 190 kHz~250 kHz and 900 kHz~1.6 MHz. An arc detection circuit with low cut off frequency of 170 kHz to attenuate 60 Hz by 170 dB and a signal discriminator were designed. Also, an algorithm which separate series arc signal from unwanted noises produced by switching operation, inverter, and surge was proposed. Application experiment was carried out on several types of air-conditioners by using the arc generator specified in UL1699, and the results showed the over 99 % accuracy.

• Journal of IKEEE
• /
• v.17 no.3
• /
• pp.284-293
• /
• 2013

This paper describes a DC-DC boost converter for thermoelectric energy harvesting. The designed converter boosts the VDD through a start-up block from a low-output voltage of a thermoelectric device and the boosted VDD is used to operate the internal control block. When the VDD reaches a predefined value, a detector circuit makes the start-up block turn off to minimize current consumption. The final boosted VOUT is achieved by alternately operating the DC-DC converter for VDD and the main DC-DC converter for VOUT according to the comparator outputs. Simulation results shows that the designed converter generates 2.65V from an input voltage of 200mV and its maximum power efficiency is 63%. The area of the chip designed using a 0.35um CMOS process is $1.3mm{\times}0.7mm$ including pads.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.12 no.5
• /
• pp.31-37
• /
• 2012

In this paper, we present a smart grid monitoring system connected with electric vehicle charging system using anti-islanding method. Electric vehicles can be charged through remote control of smart grid monitoring system and the charging process may be more stable and more efficient by wireless communication between the Local Area Module and End Modules. It is illustrated by some experiments that electric vehicle charging process may not be interrupted without any serious fault even though the islanding phenomena occurred in the grid if the presented monitoring system was applied to the smart grid system.

• The Bulletin of The Korean Astronomical Society
• /
• v.35 no.2
• /
• pp.56.1-56.1
• /
• 2010

MIRIS(Multipurpose InfraRed Imaging System)는 과학기술위성 3호의 주 탑재체로서 2011년 발사예정인 다목적 적외선 카메라 시스템이다. MIRIS는 우주관측 카메라와 지구관측 카메라로 구성되어 있으며, 우주관측 카메라는 $0.9-2.0{\mu}m$ 영역에서 3.67 deg. x 3.67 deg. FOV로 우리 은하평면 survey 관측과 우주배경복사(CIB) 관측을 수행할 것이다. 현재 MIRIS는 비행모델 개발 마무리 단계에 있으며, 검교정 시험, 열-진공 시험, 진동 시험 등을 수행하고 나면 2010년 말 위성 본체와의 조립을 진행할 것이다. 우주관측 카메라는 궤도상에서 태양, 지구의 적외선 복사와 망원경과 검출기 주변에서 발생하는 열잡음을 줄이기 위해 냉각이 필요하며, 제한된 위성의 무게와 부피, 전력등의 요구조건들 때문에 망원경 및 구조체의 복사냉각(Passive Cooling) 방법을 선택하였다. Passive cooling으로 우주관측 카메라의 망원경이 200K 이하로 냉각되면, dewar에 설치된 소형 냉각기를 가동하여 적외선 센서를 80K로 냉각한다. 위성체 내벽과 우주관측카메라의 각 구조체들 사이의 복사를 차단하기위해 30층의 MLI를 적용 하였고, 각 구조체들간의 열전도를 최소화하기위해 GFRP supporter를 적용하였다. 이 실험은 천문(연)에서 자체 제작한 열-진공 챔버를 활용하여 진행하였으며, 이미 인증모델에 대한 passive cooling 실험을 두 차례 실시하였고, 그 실험 결과를 반영하여 최종 비행모델에 대한 실험을 수행하였으며, 그 실험 결과에 대해 논의 하고자 한다.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.38 no.10
• /
• pp.754-764
• /
• 2001

Class A bipolar second-generation current conveyor (CCII) with low current-input impedance and its offset-compensated CCII for high-accuracy current-mode signal processing are proposed. The CCIIs consist of a regulated current-cell for current input, a emitter follower for voltage input, and a cascode current mirror lot current output. In these architecture, the two input stages are coupled by current mirror to reduce the current input impedance. Experiments show that the CCII has impedance of 8.4 Ω and offset voltage of 40 mV at current input terminal. To reduce this offset, the offset-compensated CCII adopts diode-connected npn and pnp transistor in the proposed CCII. Experiments show that the offset-compensated CCII has current input impedance of 2.1 Ω and offset voltage of 0.05 mV. The 3-dB cutoff frequency of the CCIIs when used as a voltage follower extends beyond 30 MHz. The power dissipation is 7.0 mW

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.39 no.11
• /
• pp.34-39
• /
• 2002

In this paper, we proposed novel photonic bandgap(PBG) structure using EGP(Elevated Ground Plane) and via in ceramic substrate of microstrip line. From analysis result, the proposed PBG structure is reduced 52.5% at size and increased 45 % at bandwidth compared to typical planar PBG structure. It is also reduced 32 % at size and improved more than 8 dB at power loss compared to typical multilayer DGS(Defected Ground Structure). The proposed PBG structure also can be used bandstop and lowpass filter and it will be useful for small microwave integrated circuit and module development.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.40 no.12
• /
• pp.46-53
• /
• 2003

This paper describes a new linear operational transconductance amplifier (OTA) and its application to the 9th-order Bessel filter. To improve the linearity of the OTA, we employ a mobility compensation technique. The combination of the triode and the subthreshold region transistors can compensate the mobility reduction effect and make the OTA with a good linearity. The proposed OTA shows $\pm$0.32% Gm variation over the input range of $\pm$0.8-V. The total harmonic distortion (THD) was lower than -60-㏈. The 9th-order Bessel filter has been designed using a 0.35-${\mu}{\textrm}{m}$ n-well CMOS process under 3.3-V supply voltage. It shows the cutoff frequency of 8-MHz and the power consumption of 65-mW.