실시간으로 적응빔형성 및 신호처리를 수행하는 평면능동위상배열 레이더 시스템 개발

김관성,이민준,정창식,염동진,Kim, Kwan Sung,Lee, Min Joon,Jung, Chang Sik,Yeom, Dong Jin 한국군사과학기술학회 2012 한국군사과학기술학회지 Vol.15 No.6

Interference and jamming are becoming increasing concern to a radar system nowdays. AESA(Active Electronically Steered Array) antennas and adaptive beamforming(ABF), in which antenna beam patterns can be modified to reject the interference, offer a potential solution to overcome the problems encountered. In this paper, we've developed a planar active phased array radar system, in which ABF, target detection and tracking algorithm operate in real-time. For the high output power and the low noise figure of the antenna, we've designed the S-band TRMs based on GaN HEMT. For real-time processing, we've used wavelenth division multiplexing technique on fiber optic communication which enables rapid data communication between the antenna and the signal processor. Also, we've implemented the HW and SW architecture of Real-time Signal Processor(RSP) for adaptive beamforming that uses SMI(Sample Matrix Inversion) technique based on MVDR(Minimum Variance Distortionless Response). The performance of this radar system has been verified by near-field and far-field tests.

레이다 성능 안정화를 위한 잡음 AGC

김관성,Kim, Kwan-Sung 한국군사과학기술학회 2007 한국군사과학기술학회지 Vol.10 No.4

The dynamic range of the radar which uses digital signal processors is limited by ADC(Analog-to-Digital Converter). That parameter and ADC loss depend on the noise level of radar receiver. In order to stabilize the performance of radar systems, it is necessary to maintain the noise level constantly. This paper presents the noise AGC(Automatic Gain Control) concept that can keep the noise level constantly and proves that the concept is acceptable through the hardware test and evaluation.

다중경로 환경에서 다중빔 탐색레이더에 적용 가능한 표적 고각오차 혼성 보정 기법

김관성,정명수,정창식,Kim, Kwan Sung,Chung, Myung Soo,Jung, Chang Sik 한국군사과학기술학회 2013 한국군사과학기술학회지 Vol.16 No.3

The multibeam surveillance radar is a state-of-art of 3D radar technology. It applies the stacked beams realized by a digital beamformer. In this paper, a hybrid compensation technique on elevation angle errors for low elevation angle targets over the sea in multipath radar environments is proposed. The proposed method can be applied to stacked beam radars. Double null algorithm based on maximum likelihood method in 3-D beamspace domain works well unless the phase difference between the two rays(direct and specular path) is close to $0^{\circ}$ and the magnitude of reflection coefficient is close to 0. To overcome these problems, we propose a hybrid compensation technique which uses the selective double null algorithm and the beam-ratio compensation technique for low-elevation errors on a log scale. Results of computer simulation show that the proposed method outperform conventional monopulse method and double null algorithm only under various multipath environments.

PGA(Phase Gradient Autofocus)기반 ISAR영상 자동초점기법 성능개선

김관성,양은정,김찬홍,박성철,Kim, Kwan Sung,Yang, Eun Jung,Kim, Chan Hong,Park, Sung Chul 한국군사과학기술학회 2014 한국군사과학기술학회지 Vol.17 No.5

PGA(phase gradient autofocus) has been widely used to remove motion induced phase errors in the ISAR(inverse synthetic aperture radar) imaging. The critical process for the processing time and image quality is windowing stage in PGA. In this paper, the new method to determine window size based on polynomial least square approximation is proposed. Moreover, dominant range bins are selected for efficient phase error estimation, which improve image quality and speed up convergence. The simulation results show that the proposed algorithm provides high quality ISAR images while computational efficiency of inherent PGA is retained.

환원법에 의한 직접 메탄올 연료전지(DMFC)용 Pt-Bi/Carbon 전극제조

김관성 ( Kwan Sung Kim ),김민경 ( Min Kyung Kim ),노동균 ( Dong Kyun Noh ),탁용석 ( Yong Sug Tak ),백성현 ( Sung Hyeon Baeck ) 한국공업화학회 2011 공업화학 Vol.22 No.5

다양한 비율의 Pt와 Bi를 carbon black (Vulcan XC-72R)에 담지시킨 Pt-Bi/C 촉매를 환원법을 이용하여 합성하였다. Pt와 Bi의 전구체로는 염화백금산(H2PtCl6 ·xH2O)과 비스무스트리질산(Bi(NO3)3 ·5H2O) 수용액을 각각 사용하였으며, 금속을 carbon에 담지하기 전, 금속물질의 분산도를 높여주기 위해 열처리와 산처리를 수행한 carbon black을 사용하였다. XRD (X-ray Diffraction) 분석과 XPS (X-ray Photoelectron Spectroscopy) 분석을 통하여 Pt-Bi/C 촉매 내에 Pt와 Bi가 소성 시키기 전에는 BiPt 혹은 Bi2Pt로 존재하지만 500 ℃에서 소성을 한 후에는 Pt 격자구조 안으로 Bi가 침투하여 alloy을 형성하는 것을 확인하였다. 합성한 전극의 메탄올 산화반응은 전기화학분석장치(Potentiostat; Princeton applied research, VSP)를 사용하여 0.5 M CH3OH와 0.5 M H2SO4의 혼합수용액에서 순환전압법(cyclic voltammetry, CV)을 이용해 측정하였다. 메탄올 산화에 대한 전기화학적 촉매 활성을 평가한 결과 적절한 양의 Bi를 첨가한 경우, 메탄올 산화반응에 대한 높은 촉매활성을 나타냄을 확인하였다. 메탄올 산화에 대한 활성은 전극과 전해질 사이의 안정성과 밀접한 관련이 있다. 정전압법(Chronoamperometry, CA)을 이용하여 전극의 안정성을 평가한 결과 메탄올 산화반응에 높은 활성을 나타내는 촉매일수록 전극의 안정성도 높은 것을 확인하였다. Pt-Bi/C catalysts supported on carbon black with various Pt/Bi ratios were synthesized by a reduction method. Chloroplatinic acid hydrate (H2PtCl6 ·xH2O) and bismuth (III) nitrate pentahydrate (Bi(NO3)3 ·5H2O) were used as precursors for Pt and Bi, respectively. Before loading metal on carbon, heat treatment and pretreatment of carbon black in an acidic solution was conducted to enhance the degree of dispersion. The physical property of the synthesized catalysts was investigated by X-ray diffraction and X-ray photoelectron spectroscopy. The XRD pattern of untreated Pt-Bi/C catalyst showed BiPt and Bi2Pt peaks in addition to Pt peaks. These results imply that Bi atoms were incorporated into the Pt crystal lattice by Pt-Bi alloy formation. The catalytic activity for methanol oxidation was measured using cyclic voltammetry in a mixture of 0.5 M H2SO4 and 0.5 M CH3OH aqueous solution. The addition of proper amount of Bi was found to significantly improve catalytic activity for methanol oxidation. The catalytic activity for methanol oxidation was closely related to the stability between electrode and electrolyte. In order to investigate the stability of catalysts, chronoamperometry analysis was carried out in the same solution at 0.6 V.

Electrodeposition of mesoporous ruthenium oxide using an aqueous mixture of CTAB and SDS as a templating agent

김경화,김관성,김길표,백성현 한국물리학회 2012 Current Applied Physics Vol.12 No.1

Mesoporous RuO2 films were electrochemically fabricated on ITO-coated glass substrate from aqueous ruthenium chloride (RuCl3$nH2O) solution. To achieve highly stable mesoporous structure, an aqueous mixture of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) was used as a templating agent. The mesoporous structure was confirmed by small angle X-ray diffraction (SAXRD) and transmission electron microscopy (TEM). The addition of small amount (10wt%) of CTAB significantly improved the stability of porous structure. The crystallinity of synthesized RuO2 thin film was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Specific capacitance of the synthesized films was evaluated by measuring cyclic voltammetry (CV) and charge-discharge curves in 0.5 M H2SO4. Compared with non-porous electrode, mesoporous RuO2 showed higher supercapacitor performance. Mesoporous RuO2 films were electrochemically fabricated on ITO-coated glass substrate from aqueous ruthenium chloride (RuCl3$nH2O) solution. To achieve highly stable mesoporous structure, an aqueous mixture of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) was used as a templating agent. The mesoporous structure was confirmed by small angle X-ray diffraction (SAXRD) and transmission electron microscopy (TEM). The addition of small amount (10wt%) of CTAB significantly improved the stability of porous structure. The crystallinity of synthesized RuO2 thin film was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Specific capacitance of the synthesized films was evaluated by measuring cyclic voltammetry (CV) and charge-discharge curves in 0.5 M H2SO4. Compared with non-porous electrode, mesoporous RuO2 showed higher supercapacitor performance.

에너지 저장용 망간 산화물 합성

신주경,김관성,탁용석,백성현 한국공업화학회 2010 한국공업화학회 연구논문 초록집 Vol.2010 No.-

수신 빔 그리드에 따른 다중경로 환경에서의 고각 추정 성능 분석

권대현,조병래,김관성,이범석 한국전자파학회 2023 한국전자파학회논문지 Vol.34 No.3

본 논문에서는 다중경로 환경에서 레이다를 이용한 고각 추정 시 수신 빔 그리드에 따라서 그 성능이 달라지는 것을확인하였다. 분석을 위해 열여섯 가지 경우의 빔 그리드를 설정하였다. 우선, 수신 빔 개수 3개와 5개의 두 가지 경우를비교하였다. 또한, 수신 빔 중첩률 0 %, 15 %, 30 %, 50 %일 때 네 가지를 비교하였다. 마지막으로, 수신 빔과 수평선의상대적 위치관계 두 가지 경우를 구분하였다. 즉, 수신 빔 중앙이 수평선에 놓일 경우와, 수신 빔 가장자리가 수평선에놓일 경우를 비교하였다. 이 열여섯 가지 경우에 대하여 각각 표적고도 세 경우를 분석하였다. SNR(signal to noise ratio) 에 따른 RMSE(root mean square error)를 구하여 고각 추정 성능을 분석하였다. 고각 추정 알고리즘은 3D BDMlL(beamspace domain maximum likelihood)을 기반으로 한 double null 알고리즘을 사용하였다. 다중경로 환경에서 저고도 표적에 대한고각 추정 시뮬레이션을 수행하여 여러 가지 빔 그리드에서의 고각 추정 오차를 분석, 비교하였다.

해상 클러터 환경에서 성능 개선을 위한 환경적응형 CFAR에 관한 연구

홍성원(Sungwon Hong),김관성(Kwan-Sung Kim),조병래(Byung-Lae Cho),김찬홍(Chan-Hong Kim) 한국정보기술학회 2021 한국정보기술학회논문지 Vol.19 No.7

This study proposes the constant false alarm rate (CFAR) method which improves the detection probability and decreases the false alarm rate under sea clutter environments. Under sea clutter environments, target signals may not be detected or a false alarm may occur due to clutter signals. Using the conventional CFAR method, the detection probability is lowered or the false alarm rate is increased depending on the surrounding environment of the target signal. To improve it, we propose a method to select the optimal CFAR method according to the environment of the target signal. The environment is estimated by calculating mean power around the test cell. Then the proposed method is confirmed by the data from the real experiment.

MPRF 레이다 시스템에서 속도 추정 오류를 감소하기 위한선별적 MTI에 관한 연구

홍성원,조병래,윤기철,김관성,김찬홍 한국정보기술학회 2022 한국정보기술학회논문지 Vol.20 No.4

본 논문에서는 MPRF 레이다에서 정확한 속도 추정을 위한 선별적 MTI 기법에 대하여 제안하였다. MPRF 레이다에서는 한 버스트에서 고속 표적에 대한 신호가 저속으로 폴드 오버(Fold over)되어 나타나므로 강한 클러터 신호가 있는 환경에서는 폴드 오버된 신호가 탐지되지 않을 수 있다. 클러터를 극복하고 탐지되더라도 클러터 스펙트럼 때문에 표적 신호의 속도 정보가 왜곡될 수 있는 가능성이 존재한다. 이는 도플러 정보를 얻기 위한 FFT 특성으로 인하여 발생하는 문제이며 이를 해결하기 위하여 MTI를 고려할 수 있다. 그러나 모든 거리 셀에 대한 MTI는 연산량이 많아지는 단점이 존재한다. 본 논문에서는 FFT 이후 탐지된 거리 셀에 대하여 선별적으로 MTI하는 방법을 제안하였다. 또한 해상 환경에서 실험을 통하여 획득된 데이터를 사용하여 제안하는 기법을 검증하였다. This study proposes the selective moving target indicator (MTI) method which estimates the precise velocity for medium pulse repetition frequency (MPRF). In MPRF radar system, because the high velocity is folded into low velocity in one burst, the folded signal cannot be detected in the strong clutter environment. Even if the target signal overcomes the clutter and is detected, there is possibility that the velocity information can be distorted. This is a problem that occurs due to the fast Fourier transform (FFT) characteristic for obtaining Doppelr information, and MTI can be considered to solve this problem. However, the MTI for all range cells has a disadvantage in that the amount of computation increases. In this paper, the method of selectively applying MTI to detected range cells is proposed. Then, the proposed method is confirmed by the data from the real experiment.