• 한국ITS학회 논문지
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• 제6권1호
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• pp.38-46
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• 2007

본 논문에서는 평면형 MMIC 공진기를 이용하여 X대역에서 동작하는 낮은 위상잡음 특성의 HBT 발진기를 설계하였다. 제안한 공진기는 기존의 분포소자를 이용한 헤어핀 공진기 면적의 1/4 수준으로 크기를 소형화를 하였다. 발진기의 측정결과 발진주파수는 8.295 GHz, 출력전력은 4.8 dBm, 위상잡음은 100 kHz 옵셋 주파수에서 -106.8 dBc/Hz와 1 MHz 옵셋 주파수에서 -121.7 dBc/Hz를 보였다.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권2호
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• pp.105-110
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• 2012

This paper designs the high-efficiency and the low-cost drive system of the smallsize electric vehicles (EVs). The power circuit for driving the dc motor is designed by considering both the cost and efficiency. In order to reduce the conduction loss of MOTFET and diode for controlling an armature voltage, some MOSFETs and diodes at the armature are in parallel connection. An operating sequence for both the field current and the armature voltage according to the accelerator pedal angle is suggested for changing smoothly the rotating direction of dc motor. Through the simulation studies, the performances of the proposed methods are verified.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2003년도 춘계 학술대회 학술발표 논문집
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• pp.283-286
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• 2003

Generally, the repeater in CDMA(Code Division Multiple Access) included HPA(HI-Power Amplifier) to amplifier communication signals. Also, HPA contained PD(Predistortor) to maintain the linearization of amplifier characteristics A configuration component of PD have been used electricity nonlinear devices such that diode. But this diode takes many influences at the circumstance temperature. Consequently, st can't maintain output linearization, and drop the communication Duality. The manufacturer set bias of the circuit to the manual at the first out of ware-house low. But the Q-point changes according to the change of the high temperature or low temperature. Therefore, we designed a system to maintain the Q-point by FDM(Fuzzy Decision Maker) in this paper.

• 센서학회지
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• 제28권1호
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• pp.7-12
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• 2019

Significant progress has been made recently in detection of highly sensitive volatile organic compounds (VOCs) using chemical sensors. Combined with the progress in design of micro sensors array and electronic nose systems, these advances enable new applications for detection of extremely low concentrations of breath-related VOCs. State of the art detection technology in turn enables commercial sensor systems for health care applications, with high detection sensitivity and small size, weight and power consumption characteristics. We have been developing an intelligent electronic nose system for detection of VOCs for healthcare breath analysis applications. This paper reviews our contribution to monitoring of respiratory diseases and to diabetic monitoring using an intelligent electronic nose system for detection of low concentration VOCs using breath analysis techniques.

• ETRI Journal
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• 제43권2호
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• pp.197-208
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• 2021

Single-carrier frequency division multiple access (SC-FDMA) is currently being used in long-term evolution uplink communications owing to its low peak-to-average power ratio (PAPR). This study proposes a new transceiver design for an SC-FDMA system based on Walsh-Hadamard transform (WHT). The proposed WHT-based SC-FDMA system has low-PAPR and better bit-error rate (BER) performance compared with the conventional SC-FDMA system. The WHT-based SC-FDMA transmitter has the same complexity as that of discrete Fourier transform (DFT)-based transmitter, while the receiver's complexity is higher than that of the DFT-based receiver. The exponential companding technique is used to reduce its PAPR without degrading its BER. Moreover, the performances of different ordered WHT systems have been studied in additive white Gaussian noise and multipath fading environments. The proposed system has been verified experimentally by considering a real-time channel with the help of wireless open-access research platform hardware. The supremacy of the proposed transceiver is demonstrated based on simulated and experimental results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권9호
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• pp.4429-4445
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• 2019

As low-power and low-rate WSNs are being widely used for industrial applications, the scheduling of such applications becomes a critical issue to guarantee meeting the stringent requirements of determinism and tight latencies. This paper studies the link scheduling problem for real-time industrial applications in time-slotted channel hopping (TSCH) networks. We propose a heuristic algorithm for centralized link scheduling referred to as path-collision aware least laxity first (PC-LLF) algorithm, which dynamically prioritizes the packets based on the laxity time to the end-to-end deadlines and the amount of collisions that messages might deal with along their designated paths to the destination device. We propose schedulability analysis of real-time applications scheduled under our prioritization approach over TSCH networks, based on the literature on real-time schedulability analysis of multiprocessors and distributed systems. We show that our methodology provides an improved schedulability condition with respect to the existing approaches. Performance evaluation studies quantify to quantify the performance of our proposed approach under a variety of scenarios.

• 한국정보전자통신기술학회논문지
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• 제12권3호
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• pp.273-281
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• 2019

국가 총에너지 소비량 중 건축물에서 소비하는 에너지는 전체의 10% 이상을 차지고 있다. 이러한 이유로 우리나라는 2025년부터 제로에너지 건물 의무화 정책을 채택하였고, 결국 건축물 에너지 절감 기술에 대한 연구가 요구되고 있다. 건축물 중 빌딩의 에너지 소비 형태를 분석해보면 조명 및 냉난방 에너지가 전체 에너지 소비량의 60% 이상을 차지하고 있는데, 이는 태양광 취득률 및 창문의 개폐 운용과 직접적인 연관이 있다. 본 논문에서는 건축물에너지 관리시스템에 취득 정보를 전송하기 위한 창호용 저전력 IoT 센서 모듈을 개발하기 위해 연구를 진행하였다. 이 모듈은 외부 환경 및 창문 개폐 상태 정보를 실시간으로 빌딩 에너지 관리 시스템에 전송하여 능동적으로 에너지 절감 조치를 취할 수 있게 네트워크를 구성하였다. 모듈에 사용되는 전력은 하베스트 에너지 중 태양광 발전을 이용한 독립적인 전원으로 설계하였다. 전원은 Buck 컨버터를 적용하여 MPPT 제어를 통해 리튬이온 배터리에 4V로 충전하는 방식으로 효율은 약 85.87%이다. 통신은 WiFi 방식을 적용하여 실시간으로 전송할 수 있도록 구성하였다. 모듈의 소비전력 저감을 위해 하드웨어 및 소프트웨어 측면에서 분석하여 저전력 IoT 센서 모듈을 구현에 대한 연구를 진행하였다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제11B권4호
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• pp.193-199
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• 2001

This paper suggests a novel single-stage drive for a switched reluctance motor (SRM) to achieve sinusoidal, near unity power factor input currents. The proposed drive is very simple without additional active switch. As a single-stage approach, which combines a DC link capacitor used as dc source and a drive used for driving the motor into one power stage, a simple structure and low cost drive in implemented. A prototype drive for an 8/6 pole SRM equipping a suitable encoder is designed to evaluate the proposed topology. Also subscription control algorithm is presented. The characteristics and validity of the proposed circuit will be discussed in depth through the experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.344-346
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• 2006

In this paper, a novel algorithm for increasing the steady state efficiency during light load operation of the induction generator that integrated with a wind power generation system is presented. The proposed algorithm based on the flux level reduction, where the flux level is estimated using Support-Vector -Machines for regression (SVR) for the optimum d-axis current of the generator. SVR is trained off-line to estimate the unknown mapping between the system's inputs and outputs, and then is used online to calculate the optimum d-axis current for minimizing generator loss. The experimental results show that SVR can define the flux-power loss accurately and determine the optimum d-axis current value precisely. The loss minimization process is more effective at low wind speed and the percent of power saving can approach to 40%.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.247-250
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• 2006

This paper presents the single-stage High Power Factor TSFC(Two-Switch Forward Converter). Recently, due to growing concern about the harmonic pollution of power distribution systems and the adoption of standards such as ICE 61000-3-2 and IEEE 519, There is a need to reduce the harmonic contents of AC line currents of power supplies. This research proposed the single-stage two switch forward circuit for low voltage and high current output. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 200W(5V, 40A) 200kHz MOSFET based experimental circuit.