• 전기학회논문지
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• 제61권11호
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• pp.1713-1719
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• 2012

In this paper, we propose a WFAN (Wireless Fighter Area Network) system based on Koinonia modems is proposed. Also, we suggest that the proposed Koinonia WFAN system is a suitable solution for indoor and outdoor wireless network of fighters. Additionally we compare the Koinonia WFAN system with the overseas ASMT (Advanced SubMiniature Telemetry). Finally we show the communication experiment results, the system requirements, and the implementation methodology of the Koinonia MFAN.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1991년도 학술발표회 논문집
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• pp.38-41
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• 1991

RLS algorithms are required for applications to adaptive line enhancers, adaptive equalizers for voiceband telephone and HF modems, and wide-badn digital spectrum mobile raio in which their convergence time and tracking speed are significant. The fast QR RLS algorithm satisfies above the requirements. Its computational complexity is linearly proportional to the tap number of a filter, N and its performance remains numerically stable. From the result of simumulation, the fast QR RLS algorithm represented Cioffi is better than gradient based algorithm in its initial performance when being applied to an adaptive line enhancer for cancelling noise.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.1001-1002
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• 2006

As most of the powerline modems use spread spectrum modulation method which has strong immunity against the narrowband fading, or psk modulation method, the amplitude of the signal contains no useful informations. In this paper, we used class D amplifier to implement the drive circuit of the analog front end, and showed that it has great superiority over other existing drive circuits in rapidly impedance changing power line channel.

• Journal of Positioning, Navigation, and Timing
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• 제13권3호
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• pp.355-363
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• 2024

Time synchronization is crucial for ensuring the reliable operation of modern economic and social infrastructures. Techniques such as Global Navigation Satellite System (GNSS)-based methods and Two-Way Satellite Time and Frequency Transfer (TWSTFT) play key roles in precise time comparison and synchronization. TWSTFT, in particular, is recognized for its ability to achieve sub-nanosecond accuracy in time transfer, making it indispensable in fields such as satellite navigation. This paper proposes a comprehensive performance evaluation method for TWSTFT modems, emphasizing pre-validation in controlled environments to mitigate operational challenges. Using the proposed evaluation method, the study presents the standard deviation of RTT according to C/N₀ and compares it with the datasheet of a commercial TWSTFT modem. Through this approach, the aim of this study is to enhance the reliability and accuracy of TWSTFT-based time synchronization across diverse applications.

• 전자공학회논문지B
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• 제32B권10호
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• pp.1338-1346
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• 1995

In this paper, we suggest the implementation of a DGPS system using two low cost commercial C/A code GPS modules and modems and its efficient operational techniques to provide DGPS service which guarantees the position accuracy of better than 10 meters for more users. The proposed DGPS system can be implemented easil at low cost because it needs a GPS module and a modem for each reference station and user. The reference station makes plans of the receiving schedule from the satellite set at each period and then provides the correction data for various satellite sets in a period. The main contribution of this paper is that users can utilize the correction data continuously and efficiently through the recursive least squares lattice filtering method. Experimental results show the position accuracy of better than 10 meters using the suggested DGPS system in almost real time.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.1125-1128
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• 1998

A new architecture for high-speed implementation of adaptive decision-feedback equalizer (ADFE) applicable to wide-band digital wireless modems is described. Rather than using conventional two's complement arithmetic, a novel complex-valued filter structure is devised, which is based on redundant binary (RB) arithmetic. The proposed RB complex-valued filter reduces the critical path delay of ADFE, as well as leads to a more compact implementation than conventional methods. Also, the carry-propagation free (CPF) operation of the RB arithmetic enhances its speed. To demonstrate the proposed method, a prototype chip set is designed. They are designed to contain two complexvalued filter taps along with their coefficient updating circuits, and can be cascaded to implement loger filter taps for high bit-rate applications.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 제13회 신호처리 합동 학술대회 논문집
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• pp.577-580
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• 2000

본 논문에서는 비동기식 Zipper 방식의 VDSL(Very High Blt-rate Digital Subscriber Line) 시스템에서 cyclic extension 을 최소화 하는 기법을 제안하고, 전형적인 전화채널 환경 하에서 제안된 방식의 성능을 분석한다. Zipper 방식에서는 각 DMT(discrete-multitone) 블록에cyclic prefix(CP) 와 cyclic suffix(CS)가 추가로 사용되는데, 여기서 CP 는 심볼간 간섭과 부채널간 간섭을 방지하기 위하여 삽입되며, CS는 upstream 과 downstream 부반송파간의 직교성을 유지하기 위하여 추가되어 near-end crosstalk (NEXT)을 방지한다. 이 방식이 동기식 Zipper 방식으로 CS에 의해 NEXT를 제거하기 위해서는 한 binder 내의 모든 송신단의 동기를 맞추어야 한다. 그러나 비동기식 Zipper 방식은 다른 송신단과의 동기가 맞지 않아 CS가 NEXT에 아무런 영향을 주지 못한다 본 논문에서는 CS를 사용하지 않는 비동기식 Zipper 방식의 VDSL 시스템을 제안한다. 컴퓨터 모의실험을 통하여 제안된 방식이 전형적인 채널환경 하에서 기존 Zipper 방식의 VDSL 시스템과 비교하여 비슷한 전송능력을 갖게 됨을 보인다.

• 대한가정학회지
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• 제42권6호
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• pp.111-121
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• 2004

This study focused on the development of creative materials by applying tapestry to produce original and high-grade dresses with consideration the modems' tendency to place high value on personal taste and style. The development remained sensitive to current trends and attempted to expand into high value-added dresses. Materials in modem fashion design, as a basis of the fashion industry, can lead to a current of new fashion and produce novel and creative ideas by stimulating the designers' creativity. Designers can diversely express a form according to their intention, since tapestry allows the expression of various feelings of texture and forms according to the combination mode of technique, structure and materials on a basic plane. Moreover, tapestry encrourages the development of varied designs because it can effectively display the texture and color of a textile surface through the careful selection of materials even under the same technique. Tapestry can apply forms similar to a textile's basic structure to fashion design and can create high added value with the merit of being 'handmade'.

• Journal of Biosystems Engineering
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• 제26권2호
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• pp.93-104
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• 2001

A linear chemigation system, integrating agrichemical appication units of pesticide and fertilizer into an irrigation system, was selected as a suitable model for the cost savings in farm management and automation. Technical designs were conducted in the areas of structure, power, drive, control, and hydraulic systems. An experimental farm was sectioned into the fields of 40m by 200m and systemized with the linear-move chemigation system of 36m in span. The chemigation system consisted of a base unit monitoring and controlling overall operation, and a driving unit traveling linearly and injecting agrichemicals. Monitoring and interlocking systems were utilized against unexpected malfunctions of power, injection and drive systems using radio freuency modems between the units. The system can be also modified to various farm sizes and stationary systems of indoor and outdoor.

• 한국국방경영분석학회지
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• 제17권2호
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• pp.123-134
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• 1991

one of the problems the users of DPS-6/45 used to face in the course of having access to work stations was that a telephone call has to be made manually every time to have receiver's modem on or off, and naturally it meant the waste of manpower as well as of time. A program has been worked out to automatically operate and control. utilizing the system clock within the main computer (DPS-6/45), the on/off switch on the modems. It has resulted in; 1) promotion in operability of the main computer, DPS-6/45 2) prevention of unnecessary telephone calls 3) curtailment of expenditure and manpower