• 대한임베디드공학회논문지
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• 제2권1호
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• pp.66-75
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• 2007

In this paper, we have propose a preamble structure and synchronization/channel estimation method for UWB-MIMO which has 960Mbps transmit rate. The proposed structure is a compatible preamble structure for synchronization/channel estimation used by MIMO in MB-OFDM(Multi-Band OFDM) systems that are one of the standard systems of MBOA. The system is compatible with MB-OFDM using the proposed preamble structure. In this paper, we argue the problem in receiver part used by MIMO technique. And we simulate the proposed preamble for using synchronization/channel estimation. The simulation result shows the same performance compared with single receiver antenna.

• 천문학회보
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• 제39권2호
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• pp.101.1-101.1
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• 2014

The fluctuation of VLBI visibility phase can be occurred, predominantly caused by the irregular distribution and motion of water vapor in the atmosphere at high frequencies (>1GHz). This radio-seeing effect shows up on filled-aperture telescopes as an anomalous refraction (AR). This can be shown as if the antenna pointing-offset increases, in other words the apparent displacement of radio sources from its nominal position happens. We carried out the single-dish observations on KVN sites in order to check the effect of AR from 2010 to 2014. Orion KL, U Her, and R Leo were observed with 1second sampling time at 22.235GHz and 43.122GHz simultaneously. Each source was observed with the tracking mode for 30 minutes per a source. We analyzed the structure function, power spectrum and Allan variance of the data according to a day and a night, a season and observatories. Finally, we can infer that the AR effect depends on the atmospheric environment, especially tropospheric turbulence.

• 한국정보통신학회논문지
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• 제7권3호
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• pp.370-377
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• 2003

MC-CDMA 방식에서는 데이터 전송 시, 서로 직교성이 있는 여러개의 부반송파들을 사용한다. 그러므로 주파수 다이버시티 효과를 얻을 수 있어서 성능이 우수한 전송이 가능하다. 본 논문에서는 에러 제어 코드 및 안테나 다이버시티를 사용했을 때의 MC-CDMA 시스템 성능을 분석하였다. 이러한 시스템에서 데이터가 다중 경로 도플러 페이딩 환경 하에서 전송될 때의 데이터 비트 에러율을 구하였다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 춘계학술대회
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• pp.52-54
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• 2011

본 논문에서는 효율적인 전자계 시뮬레이터를 구축하기 위하여 프레임워크를 설계하고 그 효용성을 검토하였다. 특히 여러 대의 네트워크 PC를 이용한 병렬화를 통하여 계산에 이용되는 PC의 수에 비례하여 계산시간이 단축되는 것을 확인하였다. 본 연구를 통하여 복잡한 구조를 가진 안테나, 공진기, 도파기 등의 설계 및 해석에 적용 가능할 것으로 기대된다.

• Journal of information and communication convergence engineering
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• 제12권2호
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• pp.67-74
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• 2014

In multi-hop communication systems, two-way relaying is one of the solutions to mitigate the spectral efficiency loss caused by a half-duplex transmission. In this paper, a simple two-way relaying scheme is proposed for two-hop two-user multiple input multiple output (MIMO) systems. In the proposed system, a base station and a relay station (RS), both equipped with two antennas, form a point-to-point MIMO channel, while the RS and two single-antenna mobile users form a point-to-multipoint multiuser (MU)-MIMO channel. Numerical examples show that the proposed system achieves a significant sum rate gain as compared to a one-way relaying system as the distance between a relay and the two users decreases. We also show that although we can expand the proposed scheme to more than two users, its performance gain as compared to that of one-way relaying decreases with an increase in the number of users.

• 한국통신학회논문지
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• 제35권7A호
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• pp.731-742
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• 2010

We propose an incremental relaying protocol in conjunction with opportunistic communication for differential modulation with an aim to make efficient use of the degrees of freedom of the channels by exploiting a imited feedback signal from the destination. In particular, whenever the direct link from the source to the destination is not favorable to decoding, the destination will request the help from the opportunistic relay (if any). The performance of the proposed system is derived in terms of average bit error probability and achievable spectral efficiency. The analytic results show that the system assisted by the opportunistic relaying can achieve full diversity at low SNR regime and exhibits a 30㏈ gain relative to direct transmission, assuming single-antenna terminals. We also determine the effect of power allocation on the bit error probability BEP) performance of our relaying scheme. We conclude with a discussion on the relationship between the given thresholds and channel resource savings. Monte-Carlo simulations are performed to verify the analysis.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.59-62
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• 1999

CDMA receiving algorithms, such as single/multi user detector and smart antenna system which have been proposed to suppress ISI and MAI. still suffer from the residual interferences among the output signals. A blind adaptive CMA post-processing technique, which is able to suppress the residual ISI and MAI symbol-by-symbol was proposed. It can be easily applied to any conventional detector at the expense of a small amount of additional computations. In this paper, a solution for the convergence problem of proposed method is proposed and analyzed. Through computer simulations it was shown that the proposed method has stable convergence property and good performance in BER.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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• pp.76-79
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• 2008

This study presents the use of multi-temporal JERS-1 SAR images to the land cover classification. So far, land cover classified by high resolution aerial photo and field survey and so on. The study site was located in Non-san area. This study developed on multi-temporal land cover status monitoring and coherence information mapping can be processing by L band SAR image. From July, 1997 to October, 1998 JERS SAR images (9 scenes) coherence values are analyzed and then classified land cover. This technique which forms the basis of what is called SAR Interferometry or InSAR for short has also been employed in spaceborne systems. In such systems the separation of the antennas, called the baseline is obtained by utilizing a single antenna in a repeat pass

• 한국군사과학기술학회지
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• 제7권3호
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• pp.93-100
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• 2004

In this paper, we describe the design, fabrication, and test results of a W-band FMCW radar for the metal target detection under the ground clutter environment. In order to detect metal targets on the ground, we used a single cassegrain antenna with the beamwidth of $1.45^{\circ}$ which forms pencil-beam footprint on the ground. A log envelope detector was applied to improve radar performance in the severe ground clutter known as Weibull and log normal clutter. The designed FMCW radar can acquire altitude information from the ground clutter with $\sigma_0=-23dB$ at the height of 160m. The fabricated W-band FMCW radar transmits 11 dBm power and the dynamic range of the receiver is from -106dBm to -30dBm. The performances of the fabricated sensors were tested out in the fields and detected a car target of 200m apart on the grass.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.91-91
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• 2000

In this paper, the error compensation method of the attitude reference system with low-cost IMU is proposed. In general, the attitude error calculated by gyro grows with time. Therefore the additional information is required to compensate the drift. The attitude angles can be bound by accelerometer mixing algorithm and the heading angle can be aided by GPS velocity information. The Kalman filter is used for error compensation. The result is verified by comparing with the attitude calculated by medium-grade IMU, LP-81.