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간단한 구조의 고조파 정합 네트워크를 갖는 GaN-HEMT 고효율 Doherty 전력증폭기
김윤재(Yoonjae Kim),김민석(Minseok Kim),강현욱(Hyunuk Kang),조수호(Sooho Cho),배종석(Jongseok Bae),이휘섭(Hwiseob Lee),양영구(Youngoo Yang) 한국전자파학회 2015 한국전자파학회논문지 Vol.26 No.9
본 논문에서는 long term evolution(LTE) 통신을 위한 2.6 GHz 대역에서 동작하는 고효율 Doherty 전력증폭기를 설계하였다. 2차 및 3차 고조파 임피던스를 조정하기 위한 간단한 구조의 정합 네트워크를 통해 전력증폭기의 고효율 동작을 달성하였다. Doherty 전력증폭기는 다양한 측면에서 장점을 갖는 GaN-HEMT 소자를 이용하여 제작되었으며, 10 MHz의 대역폭 및 6.5 dB 첨두 전력 대 평균 전력비(PAPR)의 특성을 갖는 LTE downlink 신호를 이용하여 측정되었다. 평균 전력 33.4 dBm에서 13.1 dB의 전력 이득, 57.6 %의 전력부가효율(PAE) 및 ?25.7 dBc의 인접채널누설비(ACLR) 특성을 갖는다. This paper presents a Doherty power amplifier(DPA) operating in the 2.6 GHz band for long term evolution(LTE) systems. In order to achieve high efficiency, second and third harmonic impedances are controlled using a compact output matching network. The DPA was implemented using a gallium nitride high electron mobility transistor(GaN-HEMT) that has many advantages, such as high power density and high efficiency. The implemented DPA was measured using an LTE downlink signal with a 10 MHz bandwidth and 6.5 dB PAPR. The implemented DPA exhibited a gain of 13.1 dB, a power-added efficiency(PAE) of 57.6 %, and an ACLR of ?25.7 dBc at an average output power of 33.4 dBm.
김미자(Mee-Ja Kim),김윤재(Yoonjae Kim),손은하(Eun-Ha Sohn),김금란(Kum-Lan Kim),안명환(Myung-Hwan Ahn) 한국기상학회 2008 대기 Vol.18 No.4
The occurrence and strength of the Asian Dust over the Korea Peninsular have been increased by the expansion of the desert area. For the continuous monitoring of the Asian Dust event, the geostationary satellites provide useful in-formation by detecting the outbreak of the event as well as the long-range transportation of dust. The Infrared Optical Depth Index (IODI) derived from the MTSAT-1R data, indicating a quantitative index of the dust intensity, has been produced in real-time at Korea Meteorological Administration (KMA) since spring of 2007 for the forecast of Asian dust. The data processing algorithm for IODI consists of mainly two steps. The first step is to detect dust area by using brightness temperature difference between two thermal window channels which are influenced with different extinction coefficients by dust. Here we use dynamic threshold values based on the change of surface temperature. In the second step, the IODI is calculated using the ratio between current IR1 brightness temperature and the maximum brightness temperature of the last 10 days which we assume the clear sky. Validation with AOD retrieved from MODIS shows a good agreement over the ocean. Comparison of IODI with the ground based PM 10 observation network in Korea shows distinct characteristics depending on the altitude of dust layer estimated from the Lidar data. In the case that the altitude of dust layer is relatively high, the intensity of IODI is larger than that of PM 10. On the other hand, when the altitude of dust layer is lower, IODI seems to be relatively small comparing with PMIO measurement.
MTSAT-1R 정지기상위성 자료를 이용한 전운량 산출 알고리즘 개발
이병일(Byung-Il Lee),김윤재(Yoonjae Kim),정주용(Chu-Yong Chung,),이상희(Sang-Hee Lee),오성남(Sung-Nam Oh) 한국기상학회 2007 대기 Vol.17 No.2
Cloud amount calculation algorithm was developed using MTSAT-1R satellite data. The cloud amount is retrieved at 5 km × 5 km over the Korean Peninsula and adjacent sea area. The algorithm consists of three steps that are cloud detection, cloud type classification, and cloud amount calculation. At the first step, dynamic thresholds method was applied for detecting cloud pixels. For using objective thresholds in the algorithm, sensitivity test was performed for TBB and Albedo variation with temporal and spatial change. Detected cloud cover was classified into 3 cloud types (low-level cloud, cirrus or uncertain cloud, and cumulonimbus type high-level cloud) in second step. Finally, cloud amount was calculated by the integration method of the steradian angle of each cloud pixel over 3° elevation. Calculated cloud amount was compared with measured cloud amount with eye at surface observatory for the validation. Bias, RMSE, and correlation coefficient were 0.4, 1.8, and 0.8, respectively. Validation results indicated that calculated cloud amount was a little higher than measured cloud amount but correlation was considerably high. Since calculated cloud amount has 5km × 5km resolution over Korean Peninsula and adjacent sea area, the satellite-driven cloud amount could show the possibility which overcomes the temporal and spatial limitation of measured cloud amount with eye at surface observatory.
능동 단락 사용시 영구자석 동기모터에서 발생하는 과전류와 진동 토크 저감 방법
최종원(Jongwon Choi),김윤재(Yoonjae Kim) 전력전자학회 2021 전력전자학술대회 논문집 Vol.2021 No.11
고효율의 전기모터 시스템은 전기차와 전기비행기 같은 높은 신뢰성을 요구하는 시스템에 사용되고 있다. 특히, 영구자석 동기모터는 높은 효율과 높은 파워밀도를 가지고 있어 널리 사용되고 있다. 유도모터와 다르게 영구자석형 동기 모터는 회전자에 있는 영구자석에 의하여 프리휠링 상태에서도 인버터의 DC-Link을 고전압으로 만들 수 있게 된다. 따라서 많은 전기차에서는 영구자석 동기모터를 사용하는 경우 안전상태를 능동 단락(active short circuit)으로 정의하고 있다. 이를 통하여, 능동 단락은 모터의 유기전압과 인버터의 DCLink 전압을 완벽히 분리할 수 있다. 그러나 능동 단락 시 과도상태에서 매우 큰 과전류가 유도되며 오실레이션(oscillation) 고정자 전류와 토크를 만들게 된다. 이는 인버터의 안전성에 해로운 영향을 주며 큰 진동 토크는 전기차에서 허용되기 힘든 점이다. 따라서, 본 논문은 능동 단락의 과도상태에서 프리휠링을 적절히 사용하여 과전류와 진동토크를 효과적으로 감소시키는 알고리즘을 제안하였다.
송문성(Moonsung Song),김윤재(Yoonjae Kim),정원태(Wontae Jung),강연준(Yeonjune Kang) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In these days, knowing the contributions of noise transfer path are very important to reduce noise level. The Noise Path Analysis is widely used to estimate path contributions. The operation force identification method is merged with Noise Path Analysis to predict the response noise level. There are several methods for Noise Path Analysis, the matrix inversion method is commonly used. In this paper, the matrix inversion method based on acoustic pressure is represented to replace those method based on source strength for air-borne noise. It is simulated with two acoustic sources in semi-anechoic chamber for proving its availability. The result of simulation shows good agreement with method based on source strength.
지상 및 위성 고분해 적외스펙트럼 센서에서 관측된 황사 특성
이병일(Byung-Il Lee),손은하(Eun-Ha Sohn),오미림(Mi-Lim Ou),김윤재(Yoonjae Kim) 한국기상학회 2009 대기 Vol.19 No.4
The intensive dust observation experiment has been performed at Korea Global Atmosphere Watch Center (KGAW) in Anmyeon, Korea during each spring season from 2007 to 2009. Downward and upward hyper-spectral spectrums over the dust condition were measured to understand the hyper-spectral properties of Asian dust using both ground-based Fourier Transform Infrared Spectroscopy (FT-IR) and space-borne AIRS/Aqua. To understand the impact of the Asian dust, a Line-by-Line radiative transfer model runs to calculate the high resolution infrared spectrum over the wave number range of 500-1500 ㎝?¹. Furthermore, the radiosonde, a PM10 Sampler, a Micro Pulse Lidar (MPL), and an Aerodynamic Particle Sizer (APS) are used to understand the vertical profile of temperature and humidity and the properties of Asian dust like concentration, altitude of dust layer, and size distribution. In this study, we found the Asian dust distributed from surface up to 3-4 ㎞ and volume concentration is increased at the size range between 2 and 8 ㎛. The observed dust spectrums are larger than the calculated clear sky spectrums by 15~60K for downward and lower by around 2~6K for upward in the wave number range of 800-1200 ㎝?¹. For the characteristics of the spectrum during the Asian dust, the downward spectrum is revealed a positive slope for 800-1000 ㎝?¹ region and negative slope over 1100-1200 ㎝?¹ region. In the upward spectrum, slopes are opposed to the downward one. It is inferred that the difference between measured and calculated spectrum is mostly due to the contribution of emission and/or absorption of the dust particles by the aerosol amount, size distribution, altitude, and composition.