DBS 수신기를 위한 Ku 대역 Dual-Gate Mixer의 설계

백정기 忠南大學校 産業技術硏究所 1995 산업기술연구논문집 Vol.10 No.1

A Ku-band monolithic dual-gate mixer with 0.25umx200um HEMT is designed. Simulation results reveal that 3.88dB conversion gain, 8.38dB noise figure, -13.25dB RF return loss and -15.09dB LO return loss can be obtained for 11.7GHz-12.2GHz RF frequency and 10.75GHz Lo frequency. Variation test show that the yield of 62.5% can be achieved for 10 variation of R, C, gate width and 5% variation of L. HEMT large-signal model parameters used for simulation are based on the data from the ETRI foundry.

임의의 전극 구조를 가진 광전위상변조기의 수치해석적 모델링 및 특성해석

정우영,백정기 동아대학교 공과대학 부설 한국자원개발연구소 1994 硏究報告 Vol.18 No.1

Electrooptic phase modulators are analyzed numerically by utilizing the scalar finite element method for an anisotropic diffused channel-waveguide and the surface charge concept for characterizing the electric field distribution and bandwidth performance of a given electrode geometry. The results are compared with the published data which are obtained by an approximate analytical model for electric field distribution, and the effects of electrode structure on the modulation performance are analyzed. The modeling algorithm in the paper can be applied to electrooptic modulators with arbitrary electrode geometries.

이동통신 시스템의 채널 시뮬레이션

김명기,백정기,임영도,김두영 동아대학교 공과대학 부설 한국자원개발연구소 1992 硏究報告 Vol.16 No.1

Land-mobile-radio signals are affected severely by multipath phenomena. Multipath fading may be classified into envelope fading, FM noise, and delay spread. For a bit rate of 16 kbps or higher, the effects of delay spread cannot be neglected. In this paper, BER performances of QDPSK, MSK, GMSK, and TCM-8PSK are analyzed by computer simulation under the time-selective and/or frequency-selective fading environments.

유한/경계요소법에 의한 격자결합기의 해석

김홍석,정종우,백정기 동아대학교 공과대학 부설 한국자원개발연구소 1994 硏究報告 Vol.18 No.2

A combined FEM/BEM approach is used to analyze the plane wave diffraction and coupling characteristics of rectangular gratings. The numerical results compared well with those obtained by other methods. The combined approach allows a reduction in memory size with reasonable numerical complexity, when compared with the FEM or the BEM. The algorithm can be applied to arbitrarily shaped gratings.

P2P 파일 공유 에서 효율적인 네트워크 생성

안성수,이준,이정기,박찬모 東新大學校 2003 論文集 Vol.13 No.-

The leading applications in P2P(Peer-to-Peer) file sharing are Napster, Soribada, Gnutella and Kazaa. Napster and the early version of Soribada fall into the category of centralized P2P system in which a central server provides clients with the indices of shared files and clients share those files with the help of searching feature. Previous research on this resulted in Pastry, Freenet, Chord, and CAN. A node is not connected to an arbitrary node, but the structure of network is to be maintained by mapping the node and its target contents in a certain address space. Contents that are mapped in a certain address area calls for a routing only to that specific area which brings forth the advantage of increased search efficiency. Its weak point, though, is the overload in a certain area because the discriminator which is referred to by a content or a P2P client is mapped onto a physical network.

터널 환경에서의 전파전파 특성 모델링 연구

정원정(Won-Jeong Jeong),김태홍(Tae-Hong Kim),한일탁(Il-Tak Han),최문영(Moon-Young Choi),류준규(Joon-Gyu Ryu),이호진(Ho-Jin Lee),백정기(Jeong-Ki Pack) 한국전자파학회 2009 한국전자파학회논문지 Vol.20 No.9

국내 환경의 경우, 산악 지형이 많은 지형적 특성상 수많은 터널이 존재한다. 터널은 무선 채널 환경 중 대표적인 음영지역으로서 실외 및 실내 환경의 무선 채널과는 다른 특성을 갖기 때문에 터널 환경에서의 안정된 서비스 품질을 확보하기 위해서는 전파 채널의 특성 연구가 필요하다. 특히 위성을 이용한 이동 서비스를 위해서는 터널에 의한 음영지역에서의 정상적인 위성 신호 수신이 필요하며, 이를 위해 Gap-Filler라고 하는 지상 중계기를 운영하게 되는데 이를 이용하기 위해서는 터널 환경에서의 전파전파 특성 분석을 바탕으로 한 Gap Filling 방법 연구가 필수적이다. 따라서 본 논문에서는 음영 지역에서의 정상적인 위성 신호 수신을 위하여 터널 환경에서의 ISM 대역의 전파전파 특성을 분석하고, 이를 바탕으로 효율적인 Gap Filling 방법에 대한 연구를 수행하였다. In the domestic environments, there are many tunnels since most of terrains have mountains. To ensure the quality of wireless network service in NLOS environment like tunnels which differ from indoor or outdoor wireless channels, researches on wave-propagation characteristics through such channel are necessary. Especially, in such environment the ground repeater called Gap-Fillers are usually used for satellite mobile services. To make sure that mobile service using satellites in tunnels is available, the research about Gap Filling method is essential. This research is focus on the characterising the wave-propagation through tunnels, to find the appropriate frequency, HPBW of the Gap-Filler antennas, the number of Gap-Fillers, etc. In this paper, we present the effective Gap Filling method in tunnels for ISM band, based on analysis of ray tracing and measurement results.

Path Morphology 개념을 이용한 MIMO 채널 모델링

정원정(Won-Jeong Jeong),유지호(Ji-Ho Yoo),김태홍(Tae-Hong Kim),김명돈(Myung-Don Kim),정현규(Hyun Kyu Chung),배석희(Seok-Hee Bae),백정기(Jeong-Ki Pack) 한국전자파학회 2010 한국전자파학회논문지 Vol.21 No.2

차세대 이동 통신 시스템에서는 높은 주파수 대역, 광대역, 다중 안테나(MIMO antenna)의 사용이 예상된다. 또한 무선 통신의 급격한 수요와 이동 통신 서비스의 폭발적인 증가로 인해 차세대 이동 통신 시스템의 최적화를 위한 검증 모델 개발 연구가 필요하다. 기존 MIMO 채널 모델의 경우 도심, 부도심, 시골, 개활지 등으로 포괄적으로 전파 환경을 분류하여 연구를 수행하였으나, 이러한 접근 방법은 예를 들어 도심 환경 내에서도 다양한 morphology가 존재할 수 있기 때문에 모델링 정확도 측면에서 취약성을 가질 수 있다. 본 논문에서는 path morphology 개념을 도입하여 전파 환경을 송?수신기 사이의 건물의 높이, 밀집도 등을 고려하여 세부적으로 분류하는 방법을 제안하였다. 광선 추적(ray tracing) 기법을 이용하여 각 환경별 delay spread(DS), AoD와 AoA의 angular spread(AS)를 분석하고, 이를 바탕으로 국내 환경에 적합한 MIMO 채널 모델을 제시하였다. The use of high frequency band, broad band and MIMO antenna is expected in the next generation mobile communication system. By the rapid increase of demand for wireless communications and the explosive increase of the mobile communication services, researches for optimization of next-generation mobile communication system are required. In the existing MIMO channel models, propagation-environments are commonly classified into urban, suburban, rural area, etc. However such approaches can have drawbacks in that many different morphologies may exist even in the urban area, for example. In this paper, we introduced path morphology concept, and proposed the method of morphology classification considering the building height, density, etc. Delay spread(DS), angular spread(AS) of AoD and AoA analyzed for each environment using the ray tracing technique. Based on the analysis, a MIMO channel model appropriate in domestic environment was suggested.

Heterogenous expression and protein engineering of high-active cellulase from C. thermocellum and P. Horikoshii

Mi-Ran KI,Ki Ha MIN,Tae Jeong AHN,Ki Baek YEO,Seung Pil PACK 한국생물공학회 2011 한국생물공학회 학술대회 Vol.2011 No.10

이동통신 주파수 대역에서의 동물 실험용 국부 노출 장치 개발

고채옥,박민영,도현정,김정란,정기범,백정기,Ko Chea-Ok,Park Min-Young,Doh Hyeon-Jeong,Kim Jeong-Lan,Jung Ki-Bum,Pack Jeong-Ki 한국전자파학회 2006 한국전자파학회논문지 Vol.17 No.5

본 논문에서는 이동통신 주파수 대역인 PCS와 셀룰러 대역(PCS: 1,762.5 MHz, 셀룰러: 848.5 MHz)에서 전자파의 인체 영향 규명을 위해 동물 실험용 국부 노출 장치를 설계, 제작하였다. 제작된 노출 장치는 카루셀 형의 마우스용 국부 노출 장치로서 40마리의 마우스를 동시에 노출시킬 수 있으며, 피 실험체인 마우스에 스트레스가 없도록 조명, 환기, 소음 등 환경 조건을 적절히 고려하여 제작되었다. 노출 장치의 노출량 측정을 위해 온도 프로브를 이용한 SAR측정을 수행하였다. 마우스 카데바와 고체 팬텀의 머리 부분 내부의 3점에 대해 측정하였으며, 실제로 장기간의 노출에 이용되는 조건에서 시뮬레이션 결과와 잘 일치함을 확인하였다. 현재 제작된 노출 장치는 실제 마우스의 장기 노출 실험에 사용되고 있다. We have designed local exposure systems for long-time mice experiments in PCS and cellular frequency band(PCS: 1,762.5 MHz, cellular: 848.5 MHz). The fabricated systems are local exposure systems of carousel type, and 40 mice can be exposed at a time. In order not to give extra stress to the mice ender experiment, the systems were fabricated to meet the environmental conditions such as illumination, ventilation, noise etc. SAR measurement was performed using a temperature probe. Measurements at 3 points in the head of mouse cadaver and solid phantom were made, and it has been confirmed that the measurement results are in good agreement with the simulation results in the real exposure environment. The exposure systems are currently used for long-term mice experiments.

Impact of Long-Term RF-EMF on Oxidative Stress and Neuroinflammation in Aging Brains of C57BL/6 Mice

Jeong, Ye Ji,Son, Yeonghoon,Han, Na-Kyung,Choi, Hyung-Do,Pack, Jeong-Ki,Kim, Nam,Lee, Yun-Sil,Lee, Hae-June MDPI 2018 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.19 No.7

<P>The expansion of mobile phone use has raised questions regarding the possible biological effects of radiofrequency electromagnetic field (RF-EMF) exposure on oxidative stress and brain inflammation. Despite accumulative exposure of humans to radiofrequency electromagnetic fields (RF-EMFs) from mobile phones, their long-term effects on oxidative stress and neuroinflammation in the aging brain have not been studied. In the present study, middle-aged C57BL/6 mice (aged 14 months) were exposed to 1950 MHz electromagnetic fields for 8 months (specific absorption rate (SAR) 5 W/kg, 2 h/day, 5 d/week). Compared with those in the young group, levels of protein (3-nitro-tyrosine) and lipid (4-hydroxy-2-nonenal) oxidative damage markers were significantly increased in the brains of aged mice. In addition, levels of markers for DNA damage (8-hydroxy-2′-deoxyguanosine, p53, p21, γH2AX, and Bax), apoptosis (cleaved caspase-3 and cleaved poly(ADP-ribose) polymerase 1 (PARP-1)), astrocyte (GFAP), and microglia (Iba-1) were significantly elevated in the brains of aged mice. However, long-term RF-EMF exposure did not change the levels of oxidative stress, DNA damage, apoptosis, astrocyte, or microglia markers in the aged mouse brains. Moreover, long-term RF-EMF exposure did not alter locomotor activity in aged mice. Therefore, these findings indicate that long-term exposure to RF-EMF did not influence age-induced oxidative stress or neuroinflammation in C57BL/6 mice.</P>