• Proceedings of the KIPE Conference
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• 2014.11a
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• pp.189-190
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• 2014

본 논문에서는 Proton Exchange Membrane Fuel Cell (PEMFC) 연료전지의 출력을 동기정류 방식의 벅컨버터로 변환하여 2개의 리튬 폴리머 배터리를 충전하기 위한 시스템의 디지털 제어에 관해 논의한다. 배터리의 충전시 중요한 요소인 출력 리플의 제한 조건을 만족시키도록 컨버터를 설계하고, DSP를 이용하여 이중제어 루프를 구성함으로써 충전기를 제어하였다. 컨버터 제작과 리튬전지를 이용한 충전 실험을 통해 제안한 회로와 제어기 설계 방식의 타당성을 검증하였다.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.163-166
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• 1999

In this paper, frequency synthesizer that can be used in IMT-2000 was designed and fabricated using dual loop PLL(Phase Locked Loop). For improving phase noise characteristic Voltage Controlled Oscillator was fabricated using coaxial resonator and eliminated frequency divider using SPD as phase detector and increased open loop gain. Fabricated frequency synthesizer had 1.82㎓ center frequency, 160MHz tuning range and -119.73㏈c/Hz low phase noise characteristic.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.61 no.1
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• pp.5-9
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• 2012

In this paper, multi folded dual monopole antenna for WLAN communication of dual bend is designed and fabricated. The proposed multi folded dual monopole antenna are consisted of two folded rectangle loops by microstrip fed that is modified dual monopole antenna. Therefore, the outside rectangle loop structure of the proposed antenna is extended a dual monopole. The characteristics of the proposed antenna is analyzed return loss and radiation patterns by the FDTD tools. As a result a bandwidth of proposed antenna has about 0.82GHz from 2.0 to 2.82[GHz] and 0.7GHz from 5.46 to 6.16[GHz]. It is used WLAN communications of 2[GHz] and 5[GHz].

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.3 s.357
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• pp.98-104
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• 2007

In this paper, the dual-band open loop antenna using a strip conductor for the RFID reader and Wireless LAN Application, which has a resonant frequency at 910MHz and 2.45 GHz, is proposed. Input impedance of antenna is matched with the feed line of 50 ohm by varying the length and width of sip conductor making up the antenna. The gain and directivity of antenna is enhanced as tuning the length of strip, and as also grooving the teeth shapes on the strip conductor. The size of fabricated antenna is $75mm\times100mm$. The return loss and the gain of fabricated antenna are -11.92 dB, 3.02 dBi at 910 MHz and -21.31 dB, 4.08 dBi at 2.45 GHz, respectively.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.2
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• pp.27-35
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• 2016

A Low jitter dual output frequency synthesizer for smart audio devices is described in this paper. It has been fabricated in a 1.8 V Dongbu $0.18-{\mu}m$ CMOS process. Output frequency is controlled by 3 rd order Sigma-Delta Modulation and digital divider. The frequency synthesizer has a size of $0.6mm^2$, frequency range of 0.6-200 MHz, loop bandwidth of 350 kHz, and rms jitter of 11.4 ps-21.6 ps.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.2
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• pp.134-141
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• 2010

Small PEM (Proton Exchange Membrane) fuel cell systems do not require humidification and have great commercialization possibilities. However, methods for controlling small PEM fuel cell stacks have not been clearly established. In this paper, a control method for small PEM fuel cell systems using a dual closed loop with a static feedforward structure is defined and realized using a DSP (Digital Signal Processor). The fundamental elements that need to be controlled in fuel cell systems include the supply of air and hydrogen, water management inside the stack, and heat management of the stack. For small PEM fuel cell stacks operated without a separate humidifier, fans are essential for air supply, heat management, and water management of the stack. A purge valve discharges surplus water from the stack. The proposed method controls the fan using double control loops to quicken transient response of the fan thereby improving the supply rate of air. Feedback control to compensate for the voltage change in fuel cell stack improves the response characteristics in fuel cell to load variations. The feasibility of proposed method was proved by the experiments with a 60W small PEM fuel cell system and operation of a notebook computer using this system.

• The Journal of the Korea Contents Association
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• v.13 no.11
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• pp.347-355
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• 2013

This study analyzed President Lee's speeches of Korea and the policy of SMES and ventures in the field of information technology using cognitive map analysis. The relationship analysis between policy tool variables and policy goal variables was employed to derive policy direction of IT SMEs and ventures. This paper suggests growth competence reinforcement, investment revitalization, revitalization of start-up companies, enhancement of technology competition, globalization and job creation to the policy direction of IT SMEs and ventures. In this paper, we constructed a cognitive map on the policy vision of SMEs and ventures in the field of information technology. This study also showed that this cognitive map could be characterized by a scarcity of feedback loops and a strong emphasis on the positive loops in the structure of virtuous circle.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.7
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• pp.35-44
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• 2006

When control surface failure occurs, it is conventional to correct a current control or to transform to other control. In this paper, instead of adopting a conventional way, a reconfiguration method which compensate the failure with alternative control surface deflection, depending on the level of failure, by using neural network and PCH(Pseudo-Control Hedging). The Conroller is designed of inner-loop(SCAS : Stability Command Augmentation System) with DMI(Dynamic Model Inversion) and outer-loop with Y axis acceleration feedback for a coordinate turn. Additionally, double PCH method was adopted to prevent actuator saturation and input command was generated to compensate for failure. At the end, The feasibility of the method is validated with randomly selected failure scenarios.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.2
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• pp.145-150
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• 2016

The capability of accurate positioning and tracking is necessary to implement an unmanned autonomous driving system. The moving-baseline GPS Technique is a promising candidate to mitigate positioning errors of conventional GPS system. It provides accurate positioning data based on the phase difference between received signals from multiple GPS antennas mounted on the same platform. In this paper, we propose a dual-band dual-circularly-polarized antenna suitable for the moving-baseline GPS. The proposed antenna operates at GPS L1 and L2 bands, and fed by the side of the antenna instead of the bottom. The antenna is firstly designed by calculating theoretical values of key parameters, and then optimized by means of 3D full-wave simulation software. Simulation and measurement results show that the optimized antenna offers 6.1% and 3.7% bandwidth at L1 and L2, respectively, with axial ratio bandwidth of more than 1%. The size of the antenna is $73mm{\times}73mm{\times}6.4mm$, which is small and low-profile.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.8
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• pp.865-871
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• 2010

A compact dual-band(IEEE 802.11b: 2.4~2.5 GHz, 11a: 5.15~5.825 GHz) 2-channel MIMO antenna for PMP applications is presented. The proposed antenna is composed of a planar inverted F-shape antenna(PIFA) operating at 2 GHz band and a loop antenna operating at 5 GHz band. The proposed antenna is orthogonally arranged at the edge of the ground plane for polarization and pattern diversities with excellent isolation characteristics. The two PIFA antennas operating 2 GHz have connecting line($\lambda_g$/4) face to the feed point for high isolation and low correlation at 2 GHz band. The two loop antennas connected each other in the bottom side to improve the isolation at 5 GHz band. The proposed antenna has a sufficient gain in WLAN service band and is compact sized for the portable media player (PMP) applications.