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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.
전기장 특성과 전극 형상이 다중벽 탄소나노튜브 정렬에 미치는 영향
권세훈,정영근,정창식,강명창,이형우,Kwon, Se-Hun,Jeong, Young-Keun,Jung, Chang-Sik,Kang, Myung-Chang,Lee, Hyung-Woo 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.4
In this paper, the effect of electrical characteristics and electrode shape on the alignment and attachment of multi-walled carbon nanotubes (MWNTs) has been studied. The attraction and alignment of MWNTs between the gaps has been investigated by applying electric field which is called electrophoresis and dielectrophoresis. According to the frequency of electric field, positive or negative dielectrophoretic force can be determined. The concentration of MWNTs solution was $5\;{\mu}g/ml$, and a droplet of $1.0{\sim}1.5\;{\mu}l$ was dropped between two electrodes. Through the repeated experiments, the optimal electrical conditions for aligning and attaching MWNTs in the desired places were obtained. Since the frequency range of 100 kHz~10 MHz generated positive dielectrophoretic force, MWNTs were attracted and aligned between the gaps with this frequency range. For generating enough force to attract MWNTs, the appropriate voltage range was $0.3{\sim}1.3\;V_{rms}/{\mu}m$. Furthermore, the effect of electrode shape on the alignment of MWNTs was investigated. A single MWNT attachment was accomplished on the round shaped with 70% yield.
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.