• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.8
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• pp.1090-1098
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• 2018

Many short range weather radars with the low elevation search capability are needed for analysis and prediction of unusual weather changes or rainfall phenomena which occurs regionally. However, due to the characteristics of low elevation electromagnetic wave beam, it is highly probable that the received weather signals of these radars are seriously contaminated by the ground clutter. Therefore, the filter removing low Doppler frequency band is generally used to mitigate this problem. However, the phase noise in a radar system may limit the removal of the strong clutter and this may cause serious problems in estimating weather parameters because of the remaining clutter. Therefore, in this paper, the characteristics of phase noise in a radar system are investigated and the effects of the system phase noise are analyzed in the improvement of signal to clutter ratio for the strong clutter environment such as a short and low-elevated weather radar.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.3
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• pp.475-482
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• 2023

Synthetic Aperture Radar (SAR), which provides images of targets using radio signals, enables monitoring at all times regardless of weather conditions. In this paper, the SAR system was installed on the test aircraft to collect SAR raw data on the ground and the sea, and the results of image formation using the backprojection algorithm were presented.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.12
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• pp.1292-1299
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• 2014

Weather radar systems can provide weather information of the ground, sea, and air in extensive spatial coverage in near real time. However, it becomes problematic when ground clutter signal exists around precipitation because strong signals of ground can cause a false precipitation report. A large percentage of land coverage of Korea consists of mountainous regions where ground clutter needs to be mitigated for more accurate prediction. Thus, it is considered necessary to introduce a new suitable ground clutter removal technique specifically adequate for Korea. In this paper, the C-Map(Clutter Map) method using raw radar signals is proposed for removing ground clutter using a terrain-adaptive clutter map. A clutter map is generated using raw radar signals(I/Q) of clear days, then it is subtracted from received radar signals in frequency domain. The proposed method is applied to the radar data acquired from Sobaeksan rain radar and the result shows that the clutter rejection ratio is about 91.17 %.

• Journal of The Korean Society of Grassland and Forage Science
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• v.37 no.2
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• pp.145-153
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• 2017

This study was aimed to find yield prediction model of Italian ryegrass using climate big data and geographic information. After that, mapping the predicted yield results using Geographic Information System (GIS) as follows; First, forage data were collected; second, the climate information, which was matched with forage data according to year and location, was gathered from the Korean Metrology Administration (KMA) as big data; third, the climate layers used for GIS were constructed; fourth, the yield prediction equation was estimated for the climate layers. Finally, the prediction model was evaluated in aspect of fitness and accuracy. As a result, the fitness of the model ($R^2$) was between 27% to 95% in relation to cultivated locations. In Suwon (n=321), the model was; DMY = 158.63AGD -8.82AAT +169.09SGD - 8.03SAT +184.59SRD -13,352.24 (DMY: Dry Matter Yield, AGD: Autumnal Growing Days, SGD: Spring Growing Days, SAT: Spring Accumulated Temperature, SRD: Spring Rainfall Days). Furthermore, DMY was predicted as $9,790{\pm}120$ (kg/ha) for the mean DMY(9,790 kg/ha). During mapping, the yield of inland areas were relatively greater than that of coastal areas except of Jeju Island, furthermore, northeastern areas, which was mountainous, had lain no cultivations due to weak cold tolerance. In this study, even though the yield prediction modeling and mapping were only performed in several particular locations limited to the data situation as a startup research in the Republic of Korea.

• Electronics and Telecommunications Trends
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• v.18 no.1 s.79
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• pp.33-41
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• 2003

차량용 레이더란 지능형 교통시스템의 여러 가지 구현 목표 가운데 차량의 안전 운행과 관련된 부분으로 열악한 기상조건 또는 운전자의 부주의로 인해 발생 가능한 사고를 미연에 방지할 목적으로 개발된 시스템이다. 본 고에서는 이러한 차량용 레이더에 요구되는 여러 가지 기술적인 사항들과 세계적인 업계의 동향 그리고 나아가 국내의 기술기준에서 고려해야 할 사항들에 관하여 개괄적으로 살펴보았다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.2
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• pp.109-116
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• 2014

In this paper, we propose a frequency reuse method for efficient frequency use of multi-site weather radar. Our method uses a set of orthogonal pulse compression codes and CLEAN algorithm for sidelobe interference cancellation. Computer simulation results show that performance of proposed method meet performance requirements of [1], The current S-band weather radars in South Korea use the 8 different frequency channels to avoid interference. Using proposed method, number of occupied channels can reduce from 8 to 1, the 7 frequency channels may be use for other services.

• Electronics and Telecommunications Trends
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• v.30 no.3
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• pp.84-94
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• 2015

5G와 IoT로 인한 무선 트래픽 급증에 대응하기 위해서는, 무선망 성능 및 주파수효율 향상, 신규주파수할당, 주파수 공동사용 기술 개발 등이 복합적으로 적용되어야 달성 가능하다. 그의 일환으로, LTE를 비면허 대역에 사용하려는 LTE-U(Long Term Evolution-Unlicensed)라는 새로운 패러다임의 수평적 주파수 공동사용 기술을, 이동통신에 적용하려는 시도가 진행되고 있다. LTE-A의 주파수 집성기술을 활용하여, 1차 캐리어를 면허 대역 LTE 기반으로 하고, 2차 캐리어를 비면허 대역 LTE로 묶어서 고속으로 데이터를 전송하는 기술이다. 우선적으로 5GHz 비면허 대역에 적용을 검토하고 있는데, 기존에 사용하던 Wi-Fi 및 기상레이다 등과의 공정한 공존(fair coexistence)이 가장 중요하다. 따라서 각국의 5GHz 주파수 대역 규제 현황, 공존을 위한 LBT(Listen-Before-Talk)통신 메커니즘, 표준화 현황을 살펴본다. 또한 이해 당사자인 Wi-Fi, LTE, 이용자, 기술기준의 입장을 살펴보고, 구현이슈, 지적소유권 동향 등을 검토하고, 기술적 및 정책적 대응전략을 살펴본다.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.382-382
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• 2019

홍수시 홍수관리체계는 기상청 등 관련기관으로부터 수위, 강우 등 수문자료를 취득하고, 저수지의 실시간 저수지 수위자료와 강우예측정보를 이용하여 홍수 유입량 및 방류량을 계산하고 홍수 단계별로 홍수분석을 실시한 후 조기에 상황을 전파하고 선제적으로 대응할 수 있는 운영체계가 필요하다. 본 연구에서는 기상청 레이다 및 위성자료 기반의 실시간 강우예측 자료를 적용한 저수지 홍수예측 및 하류부 침수 안전성 분석에 활용하기 위한 저수지 홍수분석 모듈을 개발하였다. 홍수량 산정은 Clark 방법과 NRCS 단위도법을 적용하고, 하류하천 수리해석을 위해 미환경청의 SWMM EXTRAN 블록을 수리해석 모형을 적용하였다. 홍수 실시간분석은 기상청 발표 예측 강우량을 이용하여 유역의 유출량을 분석하고 저수지 유입량을 산정할 수 있도록 하였으며, 이때 유입량에 의하여 저수지 홍수관리 수위를 상회하게 되면 여수토를 통하여 하류 하천으로 방류하도록 설계하였다. 방류된 홍수량은 하천을 따라 홍수추적을 수행하고 하천의 주요 지점에서 하천기본계획에서 수립된 홍수위의 상회 여부를 판단하여 관리자가 침수여부를 판단할 수 있도록 모듈을 개발하였다. 개발모듈의 검증을 위해 ${{\bigcirc}{\bigcirc}}$용수구역에 적용하여 백곡지구 농업용저수지 둑 높이기사업 기본계획(2011)에서 산정한 가능최대강수량에 대한 6시간, 12시간, 18시간, 24시간 홍수량을 HEC-HMS, HEC-1 모형으로 산정한 결과 비교하였다. 본 모듈은 농촌지역 홍수관리체계를 구축하는데 활용될 것으로 기대된다.

• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.4
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• pp.389-395
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• 2014

This technical note describes about the base stages of technology implementation for establishing "Early Warning System for Weather Hazard Management in Climate-smart Agriculture" to national onsite service. First of all, a special weather report service at catchment was represented sequential risk of 810 units of catchment by spatial statistical methods to existing 150 counties units special weather report released in KMA. The second, chronic hazard alarm service based on daily data of 76 Synoptic stations was monitor about 810 Catchment of mid-long term lapse weather and represented as a relative risk index chronic hazard risk of this time in preparation for the climatological normal conditions in the same period. Finally, we establish the foundation for delivering individually calculated field specific in hazard risk about volunteer farmer of early warning service demonstration area in seomjin downstream watershed. These three types of information were built a near real-time map service on the VWORLD background map of Ministry of Land as superposed layers nationwide catchment and demonstration areas within the farm unit weather hazard.

• Journal of Satellite, Information and Communications
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• v.12 no.3
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• pp.63-68
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• 2017

SAR(Synthetic Aperture Radar) uses electromagnetic signals to acquire ground information and has been used for wide coverage reconnaissance missions regardless of weather conditions. However SAR is known to be vulnerable to interference signals by other communication devices or radar instruments and may suffer from undesirable performance degradations and image quality. In this paper, a modified Eigen-subspace based filter is proposed that can be easily applied to SAR images affected by interference signals. The method of constructing Eigen-subspace based filter is briefly described and various simulations are performed to show the performance of the interference mitigation process. The suppression filter is applied to a ALOS PALSAR raw data affected by interfering signals in order to verify its superiority over the Notch filter.