• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.1
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• pp.48-58
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• 2012

New digital predistortion technique is proposed for power amplifier linearization in multi-band transmission systems. We consider a system where muli-band signals are combined and amplified by a single power amplifier (PA). In this system, the PA output is distorted by the nonlinear cross-products between different band signals as well as their own nonlinear self-products. To compensate these nonlinear effects, we propose a multiple PD structure. Each PD removes the nonlinear cross-products and self-products to mitigate the spectral regrowth for the corresponding band. Since the PD parameters for different bands are linked together, it is difficult to find the PD parameters separately. Thus, we propose an iterative method for finding the PD parameters jointly. For demonstration of the proposed method, multi-band characteristics of PA are extracted from a commercial power amplifier. Computer simulation was executed based on the PA parameters. The simulation results show that the proposed method can effectively linearize the PA and remove spectral regrowth at each signal band.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.12
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• pp.2165-2170
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• 2008

In this parer, it is implemented a Local distribution Audio System, based on AoIP(Audio over Internet Protocol) of a part of TCP/IP Network which belongs to Internet transmission technology. The system is controlled based on SNMP(Simple Network Management Protocol) and it is transferred to UDP as packet after changing from Analog audio sources to Digital audio sources. The implemented Local distribution Audio System have presented practical possibilities in PA system transmitting various audio sources to several areas, dispersedly and using multichannel audio like Home theaters in the limelight, recently.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.1087-1090
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• 2001

본 연구의 목적은 동아시아 지역의 NCEP 데이터를 대상으로 1000hPa, 850hPa, 700hPa, 500hPa에서의 기온, 고도와 300hPa 에서의 풍향, 풍속과 지상의 기온, 기압 데이터를 이용하여 유사 일기도 검색시 동일한 파라메터를 사용하여 유사성 정도를 검색하는 알고리즘을 개발하는데 있다. 또한 각 파라메터에 해당하는 격자 데이터로부터 특징값들을 추출하고 이를 이용하여 유사도 측정을 수행하여 유사일기도를 검색하는 알고리즘을 개발하였다.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.05a
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• pp.400-403
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• 2007

This research describes how the class D amplifiers with power efficiency are designed and implemented for the PA audio systems. The configuration that makes use of the class D amplifier properties depends strongly on their applications. Thus in this paper the characteristics of the 2-level and 3-level PWM are analysed and the circuit implementation for them is presented. Using the proposed methods, they are designed and simulated for the further investigation. Test(Simulation) results present the improved performance that shows the satisfactory operations in controlling the PWM to the input signals.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.181-182
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• 2008

In this paper, an cost-effective system architecture is proposed to implement digital predistortion scheme for linearizing the PA amplifing TDD wideband signal. To make digital predistorted signal for compensating nonlinearity of PA, a dedicated ADC and a frequency-down converter are necessary. Proposed scheme is based on the TDD feature that the RF receiver frontend is idle state during the downlink signal processing time and utilize them to make the digital predistorted signal for PA.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.3
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• pp.499-508
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• 2017

A new digital pre-distortion technique to linearize power amplifier (PA) is proposed for concurrent dual-band transmitters. In the conventional dual-band DPD techniques, two independent dual-feedback paths are required to compensate nonlinear cross-products between different bands as well as the nonlinear self-products of each band's own signal. However, it increases hardware complexity and expense. In this paper, we propose a new DPD method requiring only a single feedback path. In this new structure, the proposed technique first estimates the dual-band PA characteristics using the single feedback path. The DPD parameters are then extracted from the estimated PA characteristics. The DPD performance of the proposed method is validated through computer simulation. According to the results, the proposed technique can achieve comparable performance to the conventional two feedback DPD with significantly reduced hardware complexity.

• Journal of the Korean Vacuum Society
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• v.19 no.1
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• pp.1-9
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• 2010

A dynamic flow system has been developed which can be used for vacuum gauge calibration by comparison method - a calibration method in which the reading of the gauge under calibration is compared to another calibrated vacuum gauge called the "secondary standard" - and other vacuum-related experiments. The chamber of the calibration system is pumped by a turbomolecular pump (TMP), backed by a scroll pump. As maximum acceptable pressure at the inlet of a TMP is 0.1 Pa, above which the TMP decelerates, the pumping speed decreases and it becomes more difficult to adjust pressure under such circumstances. In the present work, high pressures of up to 133 Pa have been generated in the chamber of the newly developed dynamic flow control system by installing a well-designed conductance-reducer in the by-pass line and, at the same time, operating the TMP in safe mode. In addition, the gas flow and pressure distribution within the chamber have been investigated for the entire pressure range (0.1 Pa ~ 133 Pa) while generating pressure dynamically. Maximum deviations in pressure (1.6 %) were observed at point C on the chamber, which is close to the gas inlet port on the top of the chamber.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.96-96
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• 2012

복합분자펌프는 기존의 터보분자펌프 turbine blade에 spiral grooved를 추가하여 초고진공(10-8Pa)에서 저진공(330Pa)까지 넓은 압력범위에서 사용할 수 있고 이 펌프를 사용함으로서 완전 oil free한 진공시스템을 만들 수 있는 특징을 가지고 있다. 특히, 회전체를 비접촉으로 지지하는 자기베어링 방식을 적용함으로써, 진동은 극히 작고 베어링수명은 길면서 중저진공에 대한 배기속도가 크고 임의의 방향으로 접속이 가능하여 반도체 및 디스플레이 제조 공정과 같은 첨단산업의 다양한 분야에 쉽게 적용되고 있으며, 그 적용 분야와 시장은 계속 성장하고 있다. 고 진공과 배기 속도의 달성을 위해서, 고속으로 이동하는 격면과 기체분자를 충돌시켜, 기체 분자를 원하는 방향으로 유도하는 작동원리를 가지고 있다. 특히 공기분자의 밀도가 매우 낮은 희박가스 상태에서 고속 회전하는 blade로 공기분자를 쳐내면서 작동됨으로써 날개의 상하 압력차에 의한 공기력보다도 날개의 고속회전이 매우 중요시되고 압력으로는 10-1 Pa 이하의 분자영역에서 그 성능을 최고로 발휘할 수 있다. 이러한 복합 펌프의 주요 장점은 다음과 같다. 1. 10-8 Pa (10-10 torr) ~ 10 Pa (1 torr) 까지 넓은 영역에서 배기가 가능하다. 2. 탄화수계의 대하여 높은 압축특성을 가지고 있고, 윤활유를 사용하지 않으므로 얻을 수 있는 진공상태가 고청정하다(oil free). 3. 정밀 5축제어 자기베어링으로 완전히 부상하여 회전함으로서 마모가 없고 진동이 최소화하였을 뿐 만 아니라, 또한 운전음도 거의 없다. 4. 설치조건에 제한이 없고 고장이 거의 없다. 특히 복합분자펌프는 탄화수소화합물이 없는 진공을 생성시키면서 구성요소가 간단한 반면 폭넓은 진공대역을 충족하기 때문에 산업계와 연구계의 주요 첨단 분야에서 광범위하게 사용되고 있으며, 최근 반도체 및 디스플레이, 바이오엔지니어링 등의 발전으로 적용분야가 넓어지고 있다.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10b
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• pp.497-502
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• 1992

In this paper, a new design technique called Task Based Design (TBD) is proposed to design an optimal robot manipulator for a given task. Optimal design of a manipulator is difficult because it involves implicit and highly nonlinear functions of many design variables for a complex task. TBD designs an optimal manipulator which performs a given task best, by using a framework called Progressive Design which decomposes the complexity of the task into three steps: kinematic design, planning and kinematic control. An example of TBD is presented to demonstrate the efficiency and effectiveness of our framework.

• Journal of Aerospace System Engineering
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• v.12 no.5
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• pp.76-88
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• 2018

Space agencies such as NASA, ESA, and the US military provide guidelines and standards for PA(product assurance) requirements and plans. In recent years, major satellite manufacturers around the world have been mitigating PA requirements and processes by tailoring. PA tailoring has been implemented to improve the cost and schedule efficiency. PA tailoring can be accomplished based on various factors such as mission, classification of mission risk, complexity, development cost, life cycle, etc. In this study, PA tasks according to the mission risk classification proposed by NASA are investigated, and the tailoring method is suggested for the optimization of the development cost and schedule. In particular, the classification of mission risk for the satellites under development or operation in Korea is performed, and PA characteristics in accordance with mission risk are analyzed.