• Journal of Advanced Marine Engineering and Technology
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• 제37권1호
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• pp.99-104
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• 2013

본 논문에서는 밀리미터파에의 응용을 위하여, 소형화된 다운컨버터 MMIC(monolithic microwave integrated circuit)를 제안하였다. 구체적으로는, RF(radio frequency) 및 LO(local oscilator) 신호의 격리특성을 위해 Lange 커플러가 삽입되었고, ${\lambda}$/4 전송선로를 연결하여 역위상 RF와 동위상 LO 신호가 믹서부분 FET(field effect transistor)의 게이트에 인가되었다. 또한, IF(intermediate frequency) 출력 신호의 역위상의 결합과 LO 누설신호 제거를 위하여 역위상 결합용 능동 벌룬이 출력 포트에 설치되었다. 측정 결과에 따르면, 제안된 다운컨버터 MMIC는 양호한 RF 특성을 보였다. 구체적으로, 63 GHz의 RF 주파수와 60.6 GHz의 LO 주파수에서 IF 출력 포트에서의 LO 누설 전력이 .25 dBc, RF와 LO의 격리특성은 18 dB를 보였으며, 변환 이득이 10.3 dB를 보였다. 따라서, SAW 필터와 같은 LO 제거용 off-chip 소자는 제안된 다운컨버터 MMIC에서는 필요하지 않게 되었다. 모든 능동소자와 수동소자가 GaAs MMIC 내부에 집적되었으며, 전체 사이즈는 $2.2{\times}1.4mm^2$ 로써 초소형 MMIC가 구현되었다.

• Journal of Advanced Marine Engineering and Technology
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• 제34권2호
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• pp.325-331
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• 2010

본 논문에서는 주기적 접지구조(PPGS)를 가지는 소형 단파장의 미앤더 선로를 GaAs MMIC(Monolithic Microwave Integrated Circuit) 상에 구현하였다. PPGS구조를 이용한 미앤더 선로는 기존의 미앤더 선로에 존재하던 용량 $C_a$와 함께 추가적인 용량 $C_b$를 가짐으로써 전체적인 용량이 커지게 되어, 단파장 특성을 보여주었다. 기존의 미앤더 선로는 주기적 구조가 아닌데 반해 PPGS 구조의 미앤더 선로는 주기적 구조이므로 $\beta$값이 큰 slow-wave가 존재하며, 이로 인해 종래의 미앤더 선로에 비해 선로 상에서 훨씬 더 큰 위상변화량을 보여준다. 본 논문에서는 상기 미앤더 선로의 특성을 실험적으로 고찰하여 PPGS 구조의 미앤더 선로를 병렬 인덕터로 사용할 경우, 기존 미앤더 선로를 사용할 때 보다 높은 인덕턴스 값을 가지므로 동일한 길이의 기존 선로보다 큰 인덕턴스 값을 가지는 정합 소자로써 사용할 수 있음을 확인하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제33권1호
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• pp.144-152
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• 2009

This paper propose highly miniaturized active $90^{\circ}C$ phase difference power divider and combiner for application to wireless communication system. The conventional passive $90^{\circ}C$ power divider and combiner cannot be integrated on MMIC because of their very large circuit size. Therefore, the highly miniaturized active $90^{\circ}C$ phase difference power divider and combiner are required for a development of highly integrated MMIC. In this paper, the highly miniaturized active $90^{\circ}C$ phase difference power divider and combiner employing InGaAs/GaAs HBT were designed, fabricated on GaAs substrate. According to the results, the circuit size of fabricated active $90^{\circ}C$ phase difference power divider and combiner were $1.67{\times}0.87$ mm and $2.42{\times}1.05$ mm, respectively, which were 31.6% and 2.2% of the size of conventional passive branch-line coupler. The output gain division characteristic of proposed divider circuit showed 8.4 dB and 7.9 dB respectively, and output phase difference characteristic showed $-89.3^{\circ}C$. The output gain coupling characteristic of proposed combiner circuit showed 9.4 dB and 10.5 dB respectively, and output phase difference characteristic showed $-92.6^{\circ}C$. The highly miniaturized active $90^{\circ}C$ phase difference power divider and combiner exhibited good RF performances compared with the conventional passive branch-line coupler.

• 한국인터넷방송통신학회논문지
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• 제19권3호
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• pp.149-155
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• 2019

본 논문에서는 Ka-대역 수동위상배열탐색기에 적용할 위상 변위기를 설계하고 제작하여 성능을 확인하였다. 수동위상배열안테나에서 배열소자의 위상을 조절하여 전자 빔 조향을 수행하기 위한 핵심 소자인 위상 변위기를 설계하여 Ka-대역 1GHz 대역폭내에서 삽입손실 1.5dB이하 위상 오차 $10^{\circ}$(RMS)이내의 성능을 확인하였다. 실제 제작을 통해 확인된 성능은 배열합성 이론에 기초한 빔패턴 분석에 적용하여 추가적인 분석을 수행하였다. 검증된 위상 변위기의 최종 성능이 수동위상배열안테나 빔패턴의 성능 및 지향 오차, 각도 정확도에 미치는 영향성을 분석하여 제안된 위상 변위기 규격의 유효성을 검증하였다.

• ETRI Journal
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• 제37권1호
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• pp.128-137
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• 2015

In this work, a fishbone-type transmission line employing a comb-type ground plane (FTLCGP) was fabricated on polyethersulfone (PES) substrate, and its RF characteristics were thoroughly investigated. According to the results, it was found that the FTLCGP on PES showed periodic capacitance values much higher than other types of transmission lines due to a coupling capacitance between the signal line and ground, which resulted in a reduction of wavelength and line width. Using the theoretical analysis, we also extracted the bandwidth characteristic of the FTLCGP on PES. According to the result, the FTLCGP structure showed a cut-off frequency of 280 GHz.

• 한국지구과학회지
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• 제31권5호
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• pp.465-474
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• 2010

Real-time rainfall monitoring is of great practical importance over the highly populated Indochina area, which is prone to natural disasters, in particular in association with rainfall. With the goal of d etermining near real-time half-hourlyrain estimates from satellite, the three-layer, artificial neural networks (ANN) approach was used to train the brightness temperatures at 6.7, 11, and $12-{\mu}m$ channels of the Japanese geostationary satellite MTSAT against passive microwavebased rain rates from Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and TRMM Precipitation Radar (PR) data for the June-September 2005 period. The developed model was applied to the MTSAT data for the June-September 2006 period. The results demonstrate that the developed algorithm is comparable to the PERSIANN (Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks) results and can be used for flood monitoring across the Indochina area on a half-hourly time scale.

• 정보통신설비학회논문지
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• 제9권4호
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• pp.164-167
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• 2010

In this paper, an artificial transmission line of triangular-patch type with slots is proposed. This artificial transmission line is useful for miniaturizing the electrical lengths of conventional transmission lines. Also, this structure is easy to regulate the characteristic impedance and electrical lengths. The electrical lengths and the characteristic impedances of the proposed artificial transmission line with some parameters are researched and summarized The proposed artificial transmission line could be useful for compact designs for most of the passive microwave components. The optional-artificial transmission line is fabricated and measured at 2.45GHz.

• 전기학회논문지
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• 제56권10호
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• pp.1814-1819
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• 2007

A new active resonator using defected ground structure with islands (DGSI) is proposed. The proposed resonator is composed of the conventional microstrip line with DGSI and negative resistance of active devices. The negative resistance part is realized by field effect transistor (FET) series feedback circuits. The characteristic of the proposed resonator with DGSI is improved by combining the negative resistance part with the parallel microstrip line structure with islands, where the electric field is formed the most strongly. The measured improvement of the proposed active resonator with DGSI are 4.55dB and 0.32dB in S21 and S22, respectively, at the resonant frequency whorl it is compared to the existing passive resonator having DGSI only.

• Advances in aircraft and spacecraft science
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• 제1권1호
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• pp.15-25
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• 2014

The developed concept of smart flow control based on turbulence scale modification was applied to control a flow around a circular cylinder. The concept was realized using arrays of vortex-generators regularly spaced along a cylinder generatrix with a given step. Mechanical and thermal vortex-generators were tested, the latter having been based on the localized surface heating or plasma discharges initiated with microwave radiation near the surface. Thus depending on a particular engineering solution, flow transport properties could be modified in passive or active ways. Matched numerical and experimental investigations showed a possibility to delay flow separation and, accordingly, to improve the aerodynamic performance of blunt bodies.

• 전자공학회논문지A
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• 제33A권12호
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• pp.53-58
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• 1996

In this paper, a simple fabrication technique of an air-bridge for interconnection of isolated electrodes of microwave active and passive devices and MMIC's is proposed. The proposed air-bridge proceses are mainly combinations of thermal evaporation, positive photoresist and image reversal processes for easy lift-off of up to 2.0 .mu.m thick metal. According to the resutls of air-birdge processes, it is confirmed that air-gap and thickness of theair-bridge are about 3.5.mu.m, and 2.0.mu.m, respectively. And it is also possible to make the fine air-bridge with widths of 5~60.mu.m and post-intervals of 25~200.mu.m withot collapse. finally, GaAs power MESFET's and rectangular spiral inductors are fabricatd and measured in order to confirm of feasibility of the proposed air-bridge processes. The MAG of the fabricated power MESFET's is 10dB at 10GHz, and the inductance of the (200.mu. * 6 turns) rectangular spiral inductors 4.5 nH inX-band.