• Proceedings of the Korean Magnestics Society Conference
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• 2005.06a
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• pp.76-76
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• 2005

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.1
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• pp.79-84
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• 2020

Wireless power transfer is more convenient than wired power transfer, but has a shorter transfer distance and lower efficiency. In addition, it is difficult to charge multiple devices simultaneously. In this paper, we propose a method of magnetic beam forming by using multiple transmitters in order to increase transfer distance and improve efficiency of wireless power transfer. To do this, the relationship between the transmitter coil current and magnetic field at the center of receiver coil is modelled, and calculate the optimal transmitter coil current using the characteristics of the pseudoinverse. Finally, the validity of the proposed method is verified by simulation.

• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.697-699
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• 1999

2기가비트급 이상의 Serial-Link Chip에 적용되는 PLL의 특성은 lock-in-time이 빨라야하며 low VDD 동작을 확보해야 한다. 본 논문은 2.8기가비트급의 인터페이스 전송칩에 사용되는 PLL에 내부 전원 공급기를 설계하여 외부전원 3.3V시에 2.5V를 제공하며 이를 PFD/CP/VCO에 개별적 적용하는 제어방법 및 회로를 제안하며 이에 따르는 IPLL의 Lock-In-Time을 1mS 이내로 설계하였으며 외부동작 주파수는 100MHz이상이며 인터페이스 전송량은 2.8기가비트에 이른다. 저전압 설계를 통한 동작전류를 내부 전원 제어를 통해 순차적(Sequential Method)동작을 시킴으로 IPLL 동작시의 전류소모을 2mA이하로 제한하였다. 본 논문에서는 2.8기가비트급 인터페이스 전송칩에 적용한 IPLL의 회로 및 내부전원 공급기의 제어 방법 및 설계결과를 제안하며 이에 따르는 전송칩의 동작방법을 제안한다.

• Journal of the Korean Magnetics Society
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• v.14 no.3
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• pp.109-113
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• 2004

GMR isolator was modeled using a Wheatstone bridge which is profitable for transmitting rectangular wave digital data, and the output voltage characteristics in relation to the input current were investigated in time domain. GMR isolator modeling was divided into two parts, namely magnetic and electric parts. The flow chart of the modeling was drawn in which measured MR curve of the spin valves were incorporated to obtain the electrical voltage output. For magnetic modeling, 3-dimensional model of planar coil was analyzed by FEM method to obtain the magnetic field strength corresponding to the input current. For electric modeling, resistance, inductance and capacitance of the planar coil were calculated and magnetic field waveform was obtained corresponding to the coil current waveform in time domain. Finally, MR-H curves of spin valves and the magnetic field waveform at the spin valves were composited to obtain the output voltage waveform of the isolator. Even though the amplitude of the coil current waveform was increased by 100％, decreased by 90％, or delayed by 10％ of the period compared with the input current, similar transmitted output voltage waveform to the input current waveform was obtained due to hysteretic characteristics of the spin valves at the transmission speed of over 400 Mbit/s.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.5
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• pp.1110-1116
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• 2017

Depending on the operating characteristics, track circuit is installed for the purpose of direct or indirect control of the signal device, point switch machine and other security device. These are mainly used for train detection, transmission of information, broken rail detection and transmission of return current. Especially, the return current is related to signal system, power system and catenary line, and track circuit systems. It is one of the most important component shall be dealt for the safety of track side staff and for the protection of railway-related electrical system according to electrification. Therefore, an accurate analysis of the return current is needed to prevent the return current unbalance and the system induced disorder and failure due to an over current condition. Also, if the malfunction occurred by the return current harmonics, it can cause problems including train operation interruption. In this paper, we presented measurement and analysis method at return current and it's harmonics by high speed train operation on the honam high speed line.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.6
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• pp.34-42
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• 2011

With the progress of USN technology, fields to which wireless sensor node is applicable are increased under a condition that it holds a lot of problems to solve for betterment. One of the problems which acts as an obstacle to USN industry diffusion is the wireless sensor node battery exchange to their individual life cycle. Exchanging the battery of so many sensor nodes one by one requires a great deal of times and costs. Such problem is against the convenience supply -aim by applying USN technology. In this paper, using RF wireless power transmission system that power transmission / harvesting module from a distance of 5 m and the power of 10 dBm with a current of 1 mA or more for Sensor Nodes in lithium-polymer battery charging system tested and verified.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.1
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• pp.15-22
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• 2008

In this paper, we propose a numerical analysis on reversed current of distributed amplifier based on transmission line theory and proposed a theory to obtain optimum transmission line length to minimize the reversed currents by cancelling those components. The reversed current is analyzed as being simply absorbed into the terminal resistance in the conventional analysis. In the proposed analysis, however, they are designed to be cancelled by each other with opposite phase by the optimal length of the transmission lint Circuit simulation and implementation using pHEMT transistor were performed to validate the proposed theory with the cutoff frequency of 3.6 GHz. From the measurement, maximum gain of 14.5dB and minimum gain of 12.3dB were achieved In the operation band. Moreover, measured efficiency of the proposed distributed amplifier is 25.6% at 3 GHz, which is 7.6%, higher than the conventional distributed amplifier. Measured output power Is about 10.9dBm, achieving 1.7dB higher output power than the conventional one. Those improvement is thought to be based on the cancellation of refersed current.

• Korean Journal of Optics and Photonics
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• v.8 no.4
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• pp.327-332
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• 1997

We fabricated the high speed 1.55${\mu}{\textrm}{m}$ distributed feedback laser diodes (DFB-LD) using both two-step mesa etching process and semi-insulating InP current blocking layers. The devices characteristics were threshold current of ~15mA, slope efficiency of ~0.13mW/mA, and dynamic resistance of ~6.0Ω, with as-cleaved facets. The fabricated DFB-LD showed the single longitudinal mode with more than 40dB up to 6 $I_{th}$(CW condition), emitting at the wavelength of 0.546${\mu}{\textrm}{m}$. The -3dB bandwidth was >10㎓ at the driving current of 27mA, and the maximum -3dB bandwidth was ~18㎓ at 90 mA current, showing the superior frequency response of SI-PBH DFB-LD. In the 10Gb/s transmission experiment for 1.55${\mu}{\textrm}{m}$ DFB-LD module, maximum 10 km of single mode fiber(SMF) or 80 km of dispersion shifted fiber (DSF) could be transmitted with error free.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.217-218
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• 2016

본 논문에서는 LCCL-S 토폴로지를 가지는 무선전력전송 시스템에서 부하 및 결합계수에 따른 입력 전류 고조파를 분석한다. 분석한 입력전류의 고조파를 통하여 스위칭 손실 및 도통 손실을 예측한다. 고조파 해석의 타당성을 검증하기 위해 PSIM 시뮬레이션 및 실험을 수행한다.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.334-335
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• 2020

본 논문에서는 레이저 광원을 적용한 무선전력전송 시스템에 적용되는 PV 모듈의 출력 특성을 분석하고, PV 모듈로부터 최대 전력을 발생시키면서 배터리를 충전시킬 수 있는 컨버터 개발 결과를 제시한다. 먼저, 특정 파장에서 최대전력이 발생되도록 개발된 PV 수신모듈에 레이저 빔을 조사하였고, 레이저에 공급되는 전력 크기에 따른 PV 모듈의 전압-전류의 특성 데이터를 확보하였다. 전압/전류 특성 데이터로부터 PV 수신모듈의 소신호 저항을 분석하였고, 이를 컨버터 회로모델에 적용함으로써 제어기 설계를 위한 시스템의 전달함수를 유도하였다. 이로부터 레이저 일사량에 따른 전류원/전압원 전영역에서 PV 모듈의 입력전압을 안정적으로 제어할 수 있는 제어기를 설계함으로써 레이저 수신용 PV 모듈이 최대 전력을 발생시킬 수 있도록 하였다. 본 논문에서 제안된 방법은 MCU 제어기반 25W급 배터리 충전용 부스트 컨버터의 프로토타입 제품을 통해 실험 검증되었다.