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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.
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.
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.
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.
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.
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.
임재환(Jae-Hwan Lim),박세준(Se-Jun Park),전상미(Sang-Mi Jun),진형석(Hyung-Suk Jin),김관성(Kwan-Sung Kim),김태훈(Tae-Hun Kim),김재민(Jae-Min Kim) 한국전자파학회 2018 한국전자파학회논문지 Vol.29 No.11
현재 레이다의 발전 형태는 기존의 능동위상배열에서 디지털형 위상배열로 진화하고 있다. 디지털형 위상배열은 수신빔을 자유롭게 구성할 수 있는 장점이 있다. 이를 가능하게 하려면 각각의 복사소자별 수신신호가 디지털화되어야 한다. 본 논문에서는 이를 위한 디지털 송수신모듈을 설계 및 제작하고 시험결과를 제시하여 가능성을 확인하고자 한다. 디지털 송수신모듈은 4개의 송수신 채널을 포함한 쿼드팩 형태로 구성하였다. 고출력 송신을 위해 각 채널별로 GaN 소재의 고출력증폭소자(HPA)를 사용하였으며, 송신파형 발생과 수신신호 디지털변환을 위해 송수신 집적소자를 적용한 디지털 회로를 적용하였다. 제작한 결과, 각 채널별로 송신출력은 350 W 이상, 수신이득은 47 dB, 수신잡음지수 2 dB 이하를 만족하였다. 또한 모듈 내에서 최종 광신호로 변환된 수신출력을 저장하고, 분석하여 수신 특성을 확인하였다. Active array radar is evolving into digital active array radar. Digital active array radar has many advantages for making several simultaneous radar beams from the digital receive data of each element. A digital-type transceiver(TR) module is suitable for this goal in radar. In this work, the design results of an L-band digital TR module are presented to verify the possibility of fabrication for a digital active array antenna. This L-band digital TR module consists of a gallium-nitride-type HPA to achieve a more than 350-W peak output power and one-chip transceivers that include a digital waveform generator and analog digital converter. The receiving gain was 47 dB, the noise figure was less than 2 dB, and the final output type of the four channel receiving paths was one optic signal.
도플러 저해상도 레이다의 탐지성능 향상을 위한 속도 기반 하이브리드 도플러 처리 기법
권대현(Daihyun Kwon),조병래(Byung-Lae Cho),윤기철(Kichul Yoon),김관성(Kwan Sung Kim),김찬홍(Chan-Hong Kim) 한국정보기술학회 2023 한국정보기술학회논문지 Vol.21 No.2
In this paper, the velocity based hybrid doppler processing method is proposed to increase SIR. The proposed method uses two filters, MTI and FIR, for each velocity interval. The proposed algorithm uses a velocity boundary and two parameters are specified by Monte Carlo simulation that determine this value. The first is the ambiguity velocity which has a linear relationship with the velocity boundary. The second is the standard deviation of the FIR filter, and we investigate that it is logarithmic with the velocity boundary. Since the detection probability increases as the SIR increases, the detection performance improves as the SIR increases. Finally, the proposed algorithm was verified through simulation.