• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.207-208
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• 2007

본 논문에서는 산업용 유무선 공유 네트워크의 게이트웨이를 통한 망 구성에서 발생하는 시간 동기화 문제에 대해 분석했다. 이를 통해 적용 가능한 실시간 동기화 알고리즘을 제안했다. 또한 제안된 알고리즘의 성능 평가를 위해 기존의 동기화 알고리즘과 비교하고, 모의실험을 통해 각각의 장단점을 분석하고, 그 효용성을 검증하였다.

• Journal of Power Electronics
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• v.2 no.1
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• pp.25-31
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• 2002

Servo drives with microcomputer control provide the possibility of using modern and sophisticated control algorithms. As an additional feature it is possible to implement parallel and/or redundant software and hardware structures to realise safe motion or similar security functions. Unfortunately microcomputer control also has some impact on the behaviour of servo drives. Control algorithm, cycle time, sensors and interface have to be perfectly synchronised. Special control schemes are necessary on the line side (power supply) to meet the actual requirements concerning EMC. This contribution presents experiences and results obtained from a modern digital drive system pointing out the influences of low and high accuracy position sensors and the interdependencies mentioned above.

• Annual Conference of KIPS
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• 2016.04a
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• pp.903-906
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• 2016

최근 사물인터넷(IoT, Internet of Things)관련 기술의 발전 및 서비스 산업의 급속한 발전으로 센서 장치에 대한 수요가 증가하고 있다. 센서 장치는 사물인터넷 플랫폼과의 연동을 위한 통신 인터페이스를 필수로 지원하여야 하며, 그 외에 다양한 센서들의 연동 인터페이스와 소비 전력을 모두 고려하여 하드웨어 및 소프트웨어의 설계가 이루어져야 한다. 이와 같이 센서 장치는 베터리 소비를 최적화하여 모든 기능이 구현되어야 하므로 기능상의 제약이 많이 따른다. 시간 동기화를 위해 사물인터넷 플랫폼에서 송신하는 동기 메시지를 수신하기 위해 슬립모드를 지원하는 경우 센서 장치가 항상 깨어 있어야하므로 저전력으로 동작 할 수 없는 어려움이 따른다. 따라서 데이터를 센싱하는 주기에 맞춰 시간 동기화를 진행하는 프로토콜 및 지연 시간 계산 방안을 제시하고 이에 따른 기존 프로토콜들과 비교하여 경량화한 알고리즘을 제안한다. 향후 시간 동기화 프로토콜의 호환을 위해 CoAP 규격과 연동 될 수 있는 연구가 필요하다.

• ETRI Journal
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• v.33 no.4
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• pp.633-636
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• 2011

In this letter, we propose an overlaid hybrid division duplex (HDD) concept for cellular systems which divides a cell into inner and outer regions and utilizes the merits of both time division duplex (TDD) and frequency division duplex (FDD). The proposed system can take advantage of both TDD and FDD without handover between two duplex schemes. Moreover, it is shown that the proposed HDD system outperforms the conventional TDD or FDD system with mobile relay stations when the synchronization issue is considered in orthogonal frequency division multiple access systems. Thus, the proposed overlaid HDD can be considered as a new framework for future cellular systems.

• ETRI Journal
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• v.30 no.4
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• pp.546-554
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• 2008

Phase-locked loops (PLLs) are among the most important mixed-signal building blocks of modern communication and control circuits, where they are used for frequency and phase synchronization, modulation, and demodulation as well as frequency synthesis. The growing popularity of PLLs has increased the need to test these devices during prototyping and production. The problem of distinguishing and classifying the responses of analog integrated circuits containing catastrophic faults has aroused recent interest. This is because most analog and mixed signal circuits are tested by their functionality, which is both time consuming and expensive. The problem is made more difficult when parametric variations are taken into account. Hence, statistical methods and techniques can be employed to automate fault classification. As a possible solution, we use the back propagation neural network (BPNN) to classify the faults in the designed charge-pump PLL. In order to classify the faults, the BPNN was trained with various training algorithms and their performance for the test structure was analyzed. The proposed method of fault classification gave fault coverage of 99.58%.

• ETRI Journal
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• v.32 no.4
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• pp.503-511
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• 2010

WiBro radio frequency (RF) repeater is used for solving the problem of partial shadow areas in the wireless communication field that uses time-division duplexing (TDD) mode. In this paper, a method to efficiently generate TDD signals for WiBro RF repeater is proposed and its digital circuit is implemented. A TDD signal is detected from RF signals transmitted/received to/from RF repeater and then inputted again into the RF repeater, so that it can operate normally. First, the envelope of downlink signals is detected and then clamped to extract the basic form of a TDD signal using an operational amplifier circuit. Next, the TDD signal is generated by restoring and filtering the shape which has been distorted by the wireless channel. The algorithm and system to acquire TDD signal are developed with a goal to have simple but powerful functions with as little cost as possible. The proposed method is implemented as an RF-digital integrated system and verified through the experiments under the same condition as actual WiBro service environment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.3
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• pp.575-580
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• 2017

In these days, the big-size and high resolution multimedia file is widely used through networks. To transfer and service effectively, the internet network technology is necessary to substitute broadcasting. Normally Content Delivery Network(CDN) is widely used in conventional internet for multimedia services. But it has a small bandwidth to service. So to solve this problems, many researchers have suggest the protocol for download, content distribution/saving, server synchronization, caching, pushing rate, and streaming etc. But all of these has some defects like low resolution, packets loss and delay, real application implementations etc. So, this paper suggests a new method of network protocol based on P2P collaboration and user's content using information. And it evaluated the performance of suggested method. As the results, it showed the effectiveness of 4 performances indices : download speed, decreasing rate of connected user in same time, adaptive hit ratio, traffic decreasing rate.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.3
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• pp.388-396
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• 2010

Generally, flight information is transmitted by voice signal over legacy UHF radio in ground to air communication system. In this paper, we have implemented the transceiver of TDL(tactical data link) which transmits tactical information, such as flight information, using digital signal. For transmitting digital information over radio path, we have designed data modem that is processing CPFSK modulation, and TDMA(Time Division Multiple Access) network for Synchronization among multi user(platform). By simulating aeronautical propagation modeling with the environment of Korea terrain, it is predicted the maximum performance of communication range of the transceiver. As result of the transceiver's aviational boarding test, it is proved that the transceiver of TDL over legacy UHF radio transmits and receives the tactical information in TDMA network within communication range of 160km.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.6
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• pp.600-606
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• 1992

The series connection of power switching semiconductor elements is essential when a high voltage converter is made, so researches are being conducted to further develop this technology. In the series connection of power switching semiconductor elements, the main problem is that simultaneous conduction at turn-on and simultaneous blocking at turn-off together with voltage balancing are unattainable because of the difference of their switching characteristics. In this paper a novel series connection algorithm is proposed, which can implement not only the synchronization of the points of turn-on and turn-off time but the dynamic voltage balancing in spite of the difference of each switching characteristics. The proposed method is that the compensated control signal is attained from the voltage feedback signal and applied to the series-connected power transistors independently. Computer simulation and experimental results verify its validity.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.467-468
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• 2017

최근 수요관리를 통한 '효율적인 전력수급' 패러다임이 한창 이루어지고 있으나 신재생에너지원과 Time-shift가 가능한 ESS와 같은 최신 신설 장비를 이용한 전력운용이 대부분이다. 그러나 추가전력 설비 구축 없이 비상발전기 전력으로 에너지 수급에 적극 활용한 방안이 필요하다. 본 논문에서는 기존 비상발전기를 이용한 적극적인 전력수급이 가능한 발전기 계통연계를 위한 싱크로나이즈 시스템을 개발하였다.