다기능 레이더용 주파수합성기 개발

이희민,최재흥,한일탁,Yi, Hui-min,Choi, Jae-hung,Han, Il-tak 한국정보통신학회 2018 한국정보통신학회논문지 Vol.22 No.8

본 논문은 장거리 다기능레이더용 주파수합성기 개발에 관한 것으로 다기능레이더 체계의 기능 및 성능을 보장하기 위해 필요한 주파수합성기 성능지표를 도출하고 분석하였다. 다기능레이더는 위상배열 전자 스캔 방식을 적용한 레이더체계이고, 주파수합성기는 STALO를 포함하여 다기능레이더에 필요한 다양한 주파수신호를 합성하는 역할을 수행한다. 다기능레이더 요구사항 분석을 통해 최적의 주파수합성 방식을 선택하고, 회로크기를 포함한 성능 및 기능을 최적화하였다. 도출된 MFR용 주파수합성기 개발규격을 만족하기 위해 DDS-driven Offset-PLL(Phase Locked Loop) 방식을 사용하여 낮은 위상 잡음과 빠른 주파수 고정 시간, 우수한 불요파 특성을 갖는 주파수 합성기를 설계 및 제작하였다. 제작된 다기능 레이더용 주파수합성기는 위상잡음 -131dBc/Hz@100kHz 이하, 주파수 고정시간 $4.1{\mu}s$ 이하의 성능을 측정하였다. In this paper, we developed and then analyzed the specifications of the frequency synthesizer which was applied to long range MFR (Multi-function Radar). These specifications were able to guarantee the functions and performance of MFR. MFR was the radar system that used phase array for electronically scanning. This frequency synthesizer made various frequency signals including to STALO (Stable Local Oscillator) for MFR. By analyzing the MFR requirements, we choose the optimal frequency synthesis method and then we got the best performance and functionality including to physical size for this system. We designed and fabricated DDS (Direct Digital Synthesizer)-driven Offset-PLL (Phase Locked Loop) synthesizer to meet the requirements which were low phase noise, fast switching time and low spurious. This synthesizer had less than -131dBc/Hz@100kHz phase noise and less than $4.1{\mu}s$ switching time, respectively.

인스타그램 푸드콘텐츠 사용자의 해시태그 이용동기와 사화적 자본, 지속사용의도에 영향관계 연구

이희민,송기옥 한국호텔리조트학회 2022 호텔리조트연구 Vol.21 No.1

The purpose of this study is to 1) first explore the motivation for using hashtags for users who post or use food content on Instagram, 2) the motive of Instagram hashtag users to use social capital, the relationship connection and relationship solidarity, 3) we tried to verify the relationship between relationship connection, relationship solidarity, and intention to continue use. A Total of 272 Samples who posted Instagram hashtags within the last Three months Participated in this Study. The research results are as follows. First, as a result of factor analysis, it was classified into six factors, each of which was classified into interaction, self-expression, information sharing, identity, conspicuous expression, and storage motive. Second, as a result of regression analysis of hashtag usage motivation, social capital, and intention to continue using, it was found that interaction, information sharing, and conspicuous expression had an effect on the relational connection. Fourth, interaction, information sharing, identity, and conspicuous expression were found to affect relationship solidarity. Fifth, it was found that relational connection and relational solidarity had an effect on intention to continue use. Based on these research results, theoretical and practical implications were presented to foodservice managers, marketing managers, and practitioners through Instagram.

11세 여아에서 발생된 성숙 낭성 기형종의 염종1예

이희민,김재현,이봉주,하태규,김흥곤,윤기중 圓光大學校 醫科學硏究所 1996 圓光醫科學 Vol.12 No.1

Mature cystic teratomas comprise 10% of all ovarian tumors and show the highest frequency of incidence in women under 20 years of age. Torsion of ovarian cyst is the most common complication in young female and lower abdominal pain, peritonitis, necrosis and shock are outcomes that require emergency treatment. Generally, gross finding of mature cystic teratoma shows that most of the entire ovary is replaced by multiple cystic masses, and rarely only small portion of the ovary is changed into cystic mass. We report a case of torsion of mature cystic teratoma in an 11 year old girl with a brief review of literature.

능동위상배열 레이더 부배열 수신기 설계

이희민,김도훈,한일탁,Yi, Hui-min,Kim, Do-hoon,Han, Il-tak 한국정보통신학회 2019 한국정보통신학회논문지 Vol.23 No.5

최신의 레이더는 동시에 다양한 다수의 표적을 탐색하고, 추적하며, 외부 재밍신호를 회피할 수 있는 다기능레이더 형태로 발전하고 있다. 이러한 다기능레이더 요구사항을 만족시키기 위해서 레이더 안테나는 실시간 빔조향 뿐만 아니라 동시에 다중 빔을 형성하고, 특정 방향에 대해 수신빔 제거 등 디지털 빔 형성이 가능한 능동위상배열 안테나 형태로 구현된다. 본 논문에서는 디지털 빔 형성이 가능한 부배열 타입 배열안테나의 하드웨어 구현방안에 대해 기술하였다. 또한 배열수신빔 형성시 부엽 준위를 낮추기 위한 안테나 개구면 진폭 가중치 적용방법에 따른 부배열 수신기 설계 방법을 제시하고, 진폭 가중치 적용방법에 따른 G/T 성능을 비교하였다. 또한 설계된 부배열 마다 부배열 수신기 동적 영역에 대해 분석하고, 디지털 빔형성기의 정렬 및 보정에 더 유리한 하드웨어 구현 방안을 제시하였다. Modern Radars are evolving into MFRs which can search multiple targets simultaneously and then track them. Additionally they should be able to avoid some external jamming signals. Applying to these MFRs, Antennas should be able to perform DBF including to not only real-time beam steering but also multi-beam forming simultaneously. And they can cancel the beam at the specific direction. In this paper, we describe the implementation of sub-array type antenna hardware which can be applying DBF. Also we propose the modified amplitude aperture distribution for suppressing the side lobe level and explain the sub-array receiver design with amplitude tapering. It consists in making the amplitude weighting in 2 steps. In order to compare two weighting cases, we investigate the G/T performance for the array antenna. At the conclusion, we make a comparative study for the dynamic range of every sub-array receiver and present the hardware implementation that is more advantageous for sub-array alignment and calibration in DBF.

10W급 MEMS 스위치를 이용한 송수신모듈 소형화 개발

이희민,전병철,이복형,Yi, Hui-min,Jun, Byoung-chul,Lee, Bok-hyung 한국정보통신학회 2016 한국정보통신학회논문지 Vol.20 No.12

항공기용 능동위상배열레이다와 같이 한정된 플랫폼에 장착되는 레이다에 사용하는 부품은 소형/경량화 특성이 매우 중요하다. 또한 최근의 능동위상배열레이다는 목표물의 탐지/추적이 가능한 다목적 레이다로 사용하기 위해 수천 개의 송수신모듈이 안테나의 배열형태로 개발되며, 여기에 적용하기 위한 송수신모듈 크기와 무게는 전체 레이다를 설계하는데 중요한 요소이다. 본 논문에서는 국산화 개발된 10W급 RF MEMS 스위치를 이용하여 소형 송수신 모듈을 개발하였고, 기존에 순환기(Circulator)를 사용한 것보다 회로 면적을 약 86.5% 수준으로 줄였다. 개발된 송수신모듈은 주요 전기적 요구 성능을 만족했을 뿐만 아니라, MIL-STD의 환경시험을 통과하여 군수 부품으로 적합함을 확인하였다. 송수신모듈에 적용된 MEMS 스위치는 적응형 수신기 (Adaptive Tunable Receiver), 재구성 가능한 스마트 능동위상배열안테나(Reconfigurable smart active antenna), 광대역 빔조향 안테나 등에도 적용할 수 있다. Small size and light weight is very important for components used in radar mounted platform such as airborne radar. Recently, the active phased array radar is developed as an array of antennas for thousands of transmit/receive modules to be used as a multi-function radar that can detect and track targets. In this case, the size and weight of the transmit/receive modules are critical factor for developing the radar. In this paper, we developed a compact transmit/receive module using the 10W RF MEMS switch domestically localizing and reduced the circuit area to about 86.5% compared to using a circulator. The developed module satisfies not only electrical requirements but also MIL-STD's environmental specifications. So it can be used in a military device. It can be used at adaptive tunable receivers, reconfigurable smart active antennas and wide band beam electrical steering antennas.

카본 코팅된 Cu 금속분말의 제조 및 윤활첨가제 특성

이희민,홍현선,공만식,정항철,김건홍,박중학,이창규 한국표면공학회 2010 한국표면공학회 학술발표회 초록집 Vol.2010 No.5

입원환자의 낙상에 미치는 약물의 영향

이희민,이연미,한유정,박현자,이은경,최애리,이병구 한국의료QA학회 2008 가을학술대회 Vol.2008 No.3

Mossbauer spectroscopy and neutron diffraction of 57Fe doped TiO₂

이희민,심인보,김삼진,김철성,최용남,오화숙 한국자기학회 2002 한국자기학회 학술연구발표회 논문개요집 Vol.12 No.2

산소 결핍에 따른 Fe가 도핑된 TiO_2-δ의 상온 강자성 현상에 관한 연구

이희민,김철성,엄영랑,이창규,Lee, H.M.,Kim, C.S.,Uhm, Y.R.,Rhee, C.K. 한국분말야금학회 2006 한국분말재료학회지 (KPMI) Vol.13 No.6

Effects of oxygen deficiency on the room temperature ferromagnetism in Fe-doped reduced $TiO_2$ have been investigated by comparing the air-annealed $Ti_{0.97}Fe_{0.03}O_2$ compound with secondly post-annealed one in vacuum ambience. The air-annealed sample showed a paramagnetic behavior at room temperature. However, when the sample was further annealed in vacuum, a strongly enhanced ferromagnetic behavior was observed at same temperature. $M{\"{o}}ssbauer$ spectra of air-annealed sample at 295K showed a single doublet of $Fe^{3+}$, suggesting that the Fe ions are paramagnetic. On the other hand, the absorption spectra after vacuum-annealing exhibited two doublets, in which one is the same component with air-annealed sample and the other is new doublet corresponding to $Fe^{2+}$ state. This result suggests that the occurrence of ferromagnetism in reduced sample may be interpreted as the contribution of unquenched orbital moment of $Fe^{2+}$ ions.

함정용 추적레이더 성능 검증을 위한 모의표적신호발생장치 개발

이희민,손재현,나영진,김동환,Yi, Hui-Min,Son, Jae-Hyun,Na, Young-Jin,Kim, Dong-Hawn 한국군사과학기술학회 2012 한국군사과학기술학회지 Vol.15 No.1

The virtual target signal generator was developed to verify the shipborne tracking radar performance. It was used to DRFM(Digital RF Memory) method to generate the virtual moving targets. The target signal includes Doppler shift and RCS according to the target motion. And the signal generator can make jamming signal and clutter to test shipborne radar performance at real environmental condition. This paper described the functional diagram and the hardware configuration items to meet the test requirements for the tracking radar. And it showed the critical design points for the sub-systems. The signal generator which was developed in this paper shared the operational information of the radar with the radar command and control part. To test the frequency agility of the radar, it had the local oscillator which could do high speed frequency switching according to radar information. By communicating between the signal generator and the radar command and control part, the local oscillator of signal generator could be controlled every pulse. It reduced the instantaneous bandwidth of signal generator and minimized the spurious. So it lowered the probability of generating wrong targets.