• 한국항공운항학회지
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• 제24권1호
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• pp.10-15
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• 2016

In this study, The code-carrier divergence test was applied to GPS measurements, and the results were compared and analyzed. The GPS data used for the threshold determination were obtained from Global Navigation Satellite System permanent stations built by the Korea Aerospace Research Institute. At each permanent station, identical dual-frequency receiver and choke ring antenna with radome are installed. The analysis method, root mean square values were compared and analyzed for each permanent station and satellite. As a result, the root mean square value generally decreased as the satellite elevation angle increased although the trend was gentle. Threshold were finally selected based on the average and standard deviation of root mean square for each permanent station. For improving of availability and continuity in real-time operation when the threshold is over the limits, Code-Carrier divergence test values are initialized.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 반도체재료
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• pp.75-78
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• 2001

Recently, the HFPD measurement testing is widely used in partial discharge measurement of HV machines because HFPD measurement testing receives less influence of external noise and has a merit of good sensitivity. Also HFPD testing is able to offer the judgement standard of degradation level of HV machine and can detect discharge signals in live-line. Therefore it is very useful method compare to previous conventional PD testing method and effective diagnosis method in power transformer that requires live-line diagnosis. But partial discharges have very complex characteristics of discharge pattern so it is required continuous research to development of precise analysis method. In recent, the study of partial discharge is carrying out discover of initial defect of power equipment through condition diagnosis and system development of degradation diagnosis using HFPD(High Frequency Partial Discharge) detection. In this study, simulated transformer is manufactured and HFPD occurred from transformer is measured with broad band antenna in real time, the degradation grade of transformer is analyzed through produced patterns in simulated transformer according to applied voltages.

• 방송공학회논문지
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• 제14권1호
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• pp.89-92
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• 2009

본 논문에서는 위치인식기반 WPAN에 적용 가능한 무선인지 기술 중에서 BBA 기반의 전력할당기법에 논의한다.. Cognitive Radio 환경을 벗어난 서비스영역 밖에 있는 CR사용자의 관점에서 통신이 가능하게 하는 방법을 찾는 것이 관점이다. CR에서는 서비스 영역 밖에서는 통신을 하지 못하도록 규정을 하고 있다. 그 이유는 주사용자가 서비스를 제공받는데 피해나 간섭의 영향을 최소화하기 위해서이며, 이런 것이 선행되지 않고서는 값비싼 주파수라는 자원을 공유하기를 꺼려 하기 때문이다. 하지만 이와 같은 피해를 주지 않게 보장을 한다면 CR사용자는 서비스 영역 밖에서도 충분히 서비스를 제공받을 수 있게 된다. 그 방법을 BBA(Bi-directional Beamforming Antenna), 즉 지향성 양방향 안테나를 이용하여 가능한 방법을 제시하려 한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권3호
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• pp.1373-1392
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• 2017

WiFi Direct (WD) is a state of the art technology for a Device-to-Device (D2D) communication in 802.11 networks. The performance of the WD system can be significantly affected by some key factors such as the type of application, specifications of MAC and PHY layer parameters, and surrounding environment etc. It is, therefore, important to develop a system model that takes these factors into account. In this paper, we focus on investigating the design parameters of the PHY layer that could maximize the efficiency of the WD 802.11 system. For this purpose, a basic theoretical model is formulated for a WD network under a 2x2 Multiple In Multiple Out (MIMO) TGn channel B model. The design level parameters such as input symbol rate and antenna spacing, as well as the effects of the environment, are thoroughly examined in terms of path gain, spectral density, outage probability and Packet Error Rate (PER). Thereafter, a novel adaptive algorithm is proposed to choose optimal parameters in accordance with the Quality of Experience (QoE) for a targeted application. The simulation results show that the proposed method outperforms the standard method thereby achieving an optimal performance in an adaptive manner.

• 한국전자파학회논문지
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• 제20권9호
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• pp.989-996
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• 2009

전자파전력은 전자파 측정표준 분야의 기본 측정량이며, 관련된 주요 전자파 측정량, 예를 들면 감쇠량, RF 전압, 안테나 특성, 전자기장의 세기 등의 국가 표준을 확립하는데 직접 사용된다. 본 논문에서는 전자파전력 측정에 필요한 전자파전력계와 전력 감지기의 측정 원리를 다룬다. $50\;MHz{\sim}26.5\;GHz$의 주파수 범위에서 동작 하는 전자파전력 국가 표준 원기인 3.5 mm 등축형 미소열량계의 설계, 제작에 있어서의 핵심 사항에 대해서 다루고, 미소열량계를 중심으로 구성된 전력 측정 시스템의 구조 및 동작 원리를 고찰한다.

• 한국통신학회논문지
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• 제38A권1호
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• pp.58-67
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• 2013

본 논문에서는 빔포밍 안테나를 탑재한 이동 릴레이(MRS, Mobile Relay Station), 특히 셀 경계 근방에 위치한 이동 릴레이의 링크(link) 의 안정성을 향상시키는 방법에 대해 기술한다. OFDM 통신 방식 기반 시스템의 다중 경로 환경에서의 선형 어레이(Uniform Linear Array)를 이용한 셀 탐색 및 DoA(Direction of Arrival) 추정방법을 제안하였으며, 공간 상관 행렬 기반의 제 1 방법과 이중 차등 상관 행렬 기반의 제 2 방법의 성능을 모의실험을 통하여 평가하였다. 모의실험은 IEEE 802.16e 표준에 기반하였다.

• Journal of Positioning, Navigation, and Timing
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• 제7권3호
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• pp.183-188
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• 2018

The Global Navigation Satellite System (GNSS) signal gets delayed as it goes through the troposphere before reaching the GNSS antenna. Various tropospheric models are being used to correct the tropospheric delay. In this study, we compared effectiveness of two popular troposphere correction models: Global Pressure and Temperature (GPT) and Satellite-Based Augmentation System (SBAS). One-year data from a particular site was chosen as the test case. Tropospheric delays were computed using the GPT and SBAS models and compared with the International GNSS Service tropospheric product. The bias of SBAS model computations was 3.4 cm, which is four times lower than that of the GPT model. The cause of higher biases observed in the GPT model is the fact that one cannot get wet delays from the model. If SBAS-based wet delays are added to the hydrostatic delays computed using the GPT model, then the accuracy is similar to that of the full SBAS model. From this study, one can conclude that it is better to use the SBAS model than to use the GPT model in the standard code-pseudorange data processing.

• 천문학회지
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• 제29권spc1호
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• pp.173-174
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• 1996

We have mapped $17 deg^2$ region toward Galactic anticenter in $^{12}CO$ J = 1 - 0 using the 3 mm SIS receiver on the 14 m telescope at Taeduk Radio Astronomy Observatory (TRAO). The region mapped in this paper is the first target of the Galactic AntiCenter CO Survey Project (GACCOS) and was selected comparing with IRAS Sky Survey Atlas (ISSA) images at 100${\mu}m$. Molecular emission of the target area is found to be very extended and is well matching with the FIR emission boundary. There are several pieces of clouds, and as some of spectra show several peaks, there seem to be several clouds overlapped in some directions. The Velocity of Local Standard of Rest ($V_{LSR}$) of the CO emission of the mapped region ranges from -20 to +10 km/s. It is also found that the two cloudlets located around I = $180^{\circ}$ have $V_{LSR}$ = -20 km/s, which is very abnormal. The peak antenna temperature of 13 K arises near the H II Region S241.

• 반도체디스플레이기술학회지
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• 제14권2호
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• pp.9-16
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• 2015

In this paper, selection criterions on selection diversity are researched. The diversity is applied to the multiple antenna system based on wireless access in vehicular environment (WAVE) standard for rapid varying channel. Least squares (LS) based decision feedback equalizer (DFE) are used for channel equalization. Received signal is regenerated by means of the decision feedback path. In the selection diversity, the regenerated signal as well as the received signal is selected according to selection criterion. The decision feedback algorithm can follow the fast speed of WAVE fading channel. To control the tracking speed of the time-varying channel, simple low pass filter is used. Finally, the estimated channel value recovers the distorted payloads. Signal power before automatic gain control (AGC) in analog stage can be used as a selection criterion. In the digital stage, signal power after AGC, noise power after AGC, signal to noise ratio after AGC and cross-correlation method can be used as selection criterions. According to the simulation results, the performance of the selection diversity is improved in comparison with that of the combining diversity for the WAVE fading channel.

• 한국전자파학회논문지
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• 제11권2호
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• pp.286-293
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• 2000

본 논문은 ISO TC-204 WG-15에서 표준화를 다루고 있는 DSRC 물리 계층에서의 성능 분석 및 향상에 관해 다루었다 .. DSRC는 노변(RSU)←차량(OBE)간 거리가 100m 이하인 단거리 무선통신이며, 값싸고 저렴한 변조기 술이 요구되는데, 국내에서는 PSK. FSK. ASK 중에서 ASK가 표준 변조 방식으로 시스템이 개발되고 있다 본 논문은 개발 초기 단계에 있는 DSRC 물리계층 시스템의 라이시안 페이딩 채널하의 변조 방식별 성능 분석을 통하여 ASK 방식의 타당성 및 성능 한계성을 검증하고 아울러 성능향상을 위한 등화기 및 안테나 다이버시티 기법을 제시하고 이에 따른 성능 향상 효과를 시율레이션을 통하여 보여준다.