• Journal of electromagnetic engineering and science
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• 제18권2호
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• pp.117-128
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• 2018

In this paper, compact linear dual polarized series-fed $1{\times}2$ linear and $2{\times}2$ planar arrays antennas for airborne SAR applications are proposed. The proposed antenna design consists of a square radiating patch that is placed on top of the substrate, a quarter wave transformer and $50-{\Omega}$ matched transformer. Matching between a radiating patch and the $50-{\Omega}$ microstrip line is accomplished through a direct coupled-feed technique with the help of an impedance inverter (${\lambda}/4$ impedance transformer) placed at both horizontal and vertical planes, in the case of the $2{\times}2$ planar array. The overall size for the prototype-1 and prototype-2 fabricated antennas are $1.9305{\times}0.9652{\times}0.05106{{\lambda}_0}^3$ and $1.9305{\times}1.9305{\times}0.05106{{\lambda}_0}^3$, respectively. The fabricated structure has been tested, and the experimental results are similar to the simulated ones. The CST MWS simulated and vector network analyzer measured reflection coefficient ($S_{11}$) results were compared, and they indicate that the proposed antenna prototype-1 yields the impedance bandwidth >140 MHz (9.56-9.72 GHz) defined by $S_{11}$<-10 dB with 1.43%, and $S_{21}$<-25 dB in the case of prototype-2 (9.58-9.74 GHz, $S_{11}$< -10 dB) >140 MHz for all the individual ports. The surface currents and the E- and H-field distributions were studied for a better understanding of the polarization mechanism. The measured results of the proposed dual polarized antenna were in accordance with the simulated analysis and showed good performance of the S-parameters and radiation patterns (co-pol and cross-pol), gain, efficiency, front-to-back ratio, half-power beam width) at the resonant frequency. With these features and its compact size, the proposed antenna will be suitable for X-band airborne synthetic aperture radar applications.

• 한국군사과학기술학회지
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• 제17권4호
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• pp.485-491
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• 2014

An Antenna & RF system for a fly-away satcom terminal application on ka-band is presented in this paper. The Fly-away satellite terminal can be moved and operated by two person and adapt automatic satellite tracking system in order to decrease the tracking time. Additionally, for low-power consumption, compact size and light-weight, a dual reflector antenna is constructed using dual-offset gregorian antenna structure. For minimize weight, the reflector of the antenna is made of Magnesium. For low-power consumption and light-weight, the pHEMT MMIC compound devices is utilized. The Electronic Band-Gap(EBG) Low-Pass Filter(LPF) is designed for harmonic rejection. In the receiving part, Low-Noise Block converter(LNB) structure is designed for compact and lightweight. In this paper, fly-away satcom terminal with low-power consumption, compact size and light-weight is described with antenna system and RF system performances. Through the experimentation, fly-away terminal's EIRP is more than 50dBW, G/T is more than $17dB/^{\circ}K$.

• 한국전자통신학회논문지
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• 제8권1호
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• pp.41-47
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• 2013

본 논문에서는 두개의 브랜치 라인을 갖는 와이파이 이동통신용 이중 대역 모노폴 안테나를 설계 및 제작하였다. 제안된 안테나는 평면형 모노폴 설계를 기본으로 두 개의 브랜치 방사 선로를 구성함으로서 이중대역 특성을 갖도록 설계하였다. 제안된 안테나의 접지면 크기는 전형적인 셀룰라 ㅋ폰의 접지면에 적합하게 설계하여 이동통신용 단말기의 PCB와 호환될 수 있도록 하였다. 제안된 안테나는 최적화된 파라메타을 얻기 위해 상용 툴(CST)을 사용하여 시뮬레이션 하였으며 얻어진 최적화된 수치를 이용하여 제안된 안테나를 제작하였다. 제작된 안테나는 와이파이 이동통신의 동작하는 상위 주파수 대역과 하위 주파수 대역에서 반사손실, 이득, 방사패턴의 특성을 측정하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1929_1930
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• 2009

Fully embedded tunable bandpass filter (BPF) with inductive coupling circuits is newly designed and demonstrated for UHF TV tuner ranged from 500MHz to 900MHz receivers. Conventional RF tuning circuit with an electromagnetic coupled tunable filter has several problems such as large size, high volume, and high cost, since the electromagnetic coupled filter is comprised of several passive components and air core inductors to be assembled and controlled manually. To address these obstacles, compact tunable filter with inductive coupling circuit was embedded into low cost organic package substrate. The embedded filter was optimally designed to have high performance by using high Q spiral stacked inductors, high dielectric $BaTiO_3$ composite MIM capacitors, varactor diodes. It exhibited low insertion loss of approximately -2dB, high return loss of below -10dB, and large tuning range of 56.3%. It has an extremely compact size of $3.4{\times}4.4{\times}0.5mm^3$.

• Geomechanics and Engineering
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• 제10권1호
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• pp.109-124
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• 2016

In this paper, process of dynamic powder compaction is investigated experimentally using impact of drop hammer and die tube. A series of test is performed using aluminum powder with different grain size. The energy of compaction of powder is determined by measuring height of hammer and the results presented in term of compact density and rupture stress. This paper also presents a mathematical modeling using experimental data and neural network. The purpose of this modeling is to display how the variations of the significant parameters changes with the compact density and rupture stress. The closed-form obtained model shows very good agreement with experimental results and it provides a way of studying and understanding the mechanics of dynamic powder compaction process. In the considered energy level (from 733 to 3580 J), the relative density is varied from 63.89% to 87.41%, 63.93% to 91.52%, 64.15% to 95.11% for powder A, B and C respectively. Also, the maximum rupture stress are obtained for different types of powder and the results shown that the rupture stress increases with increasing energy level and grain size.

• 전기학회논문지
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• 제59권10호
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• pp.1850-1855
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• 2010

The application field of the pulse power is very wide. Recently, Pulse power technologies take a large place in several applications. Then, many civil and military applications proceed. Marx generator is widely used in high voltage applications. Marx generator is widely used in high voltage applications, such as eletromagnetic wave and power lasers. This paper, we described about the high voltage pulse generator. A compact size high voltage pulse generator with nanosecnd rise time has been fabricated and investigated experimentally. The marx generator has 2 stages. Each stage was constructed one charging capacitor, two electrodes and one charging resistor. A inductance structure is used in order to improve the switching performances fo the whole generator. The experiments of rise time in pure gas and mixtures of gases were described. We tested the Marx generator at different insulation gas. the results show that the dielectric strength of the $N_2-SF_6$ mixture was significantly increased compared with pure nitrogen gas. The experimental results show that the rise time characteristics of the Marx generator can be controlled through varying insulation gas.

• Journal of the Korean Data and Information Science Society
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• 제22권4호
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• pp.735-740
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• 2011

최근 전자기기의 소형화, 인텔리전트화, 다기능화, 광대역화에 관심이 집중되어 많은 발전이 이루어졌으며, 이들 전자기기들에 이용되는 모듈형의 전원장치 (SMPS : Switching-mode power supply)도 소형화, 경량화, 고효율화, 고신뢰성화, 저노이즈화를 실현하고 있다. 85~265 볼트교류전압(VAC : Voltage alternating current) 상용 전원을 공급받아 DC 출력을 공급하는 전원장치인 파워모듈은 마이크로컨트롤러, 릴레이 등 전기, 전자 회로용 전원 공급기를 간단하고 쉽게 설계하도록 개발되고 있다. 이 모듈은 전원을 사용하는 장비에 광범위하게 적용할 수 있어 에너지 절감이라는 세계적인 대과제에 적합한 제품이기는 하나 제품의 품질과 성능에 대한 통계적분석이 필요한 바 적용제품의 부하별, 출력전압별 성능분석을 하여 그 문제점을 찾아보려고 한다.

• 천문학회보
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• 제36권1호
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• pp.54.2-54.2
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• 2011

It is the conventional wisdom that the Poynting-Robertson effect is essentially the outcome of the interplay between absorption and reemission processes. For a better understanding of the motion of charged particles around a compact star with strong radiation, we reached an alternative interpretation for the Poynting-Robertson effect based on the covariant formalism and found that it is attributed to the combination of the aberration and the Lorentz transformation of the radiation stress-energy tensor. As a general relativistic application of the Poynting-Robertson effect, we studied the dynamics of test particles around the spinning relativistic star with strong radiation. We discovered that the combination of the angular momentum and the finite size of the star generates "radiation counter drag" which exerts on the test particle to enhance its specific angular momentum, contrary to the radiation drag. The balance of the radiation drag and the radiation counter drag renders the particle to hover around the spinning luminous star at the "suspension orbit". The radial position and the angular velocity of the particle on the "suspension orbit" are determined by the angular momentum, the luminosity, and the size of the central star only, and they are independent of the initial position and velocity of the particle.

• 한국전자통신학회논문지
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• 제8권7호
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• pp.979-986
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• 2013

최근, 전기, 전자, 로봇, 의료 산업 등 전 분야에서 소형화된 크기로 고도의 지적인 기능을 가지는 MEMS 기반의 스마트 디바이스 개발에 큰 관심이 집중되고 있다. MEMS 기술은 스마트 디바이스에서 요구되는 복잡한 전기적, 기계적, 화학적 그리고 생물학적 기능들을 하나로 결합하여, 초소형, 초경량으로 설계하고, 동시에 이들 디바이스들을 대량으로 일괄 제조할 수 있기 때문에 생산성 및 실용성, 경제성 측면에서 매우 효과적이다. 따라서 본 연구에서는 다가올 MEMS 기반의 새로운 기술적 패러다임에 대비하기 위해 MEMS의 공정들을 분석하고 그 적용 사례들을 고찰함으로서 기본적인 적용 방법론을 확립한다.

• 전기학회논문지
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• 제61권8호
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• pp.1159-1163
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• 2012

In this paper, a new method is suggested to reduce the size of a wide-band array antenna. The power-divider for the feeding structure is made compact as ${\lambda}/8$ with the help of a novel Metamaterial UWB bandpass filter. This power divider is clearly different from others in that the proposed design uses microstrip structured Composite Right and Left-Handed (CRLH) filters, while others use two dielectric layers or long tapered transmission lines. In order to validate the proposed design method, the circuit and full-wave simulated results of the power divider with the Metamaterial UWB filters are compared to each other, and the Metamaterial properties of the structure are shown with the electric field at the ZOR and dispersion diagram. Furthermore, the antenna performance of the fabricated antenna with the power divider is measured and compared with the prediction. Also, the size reduction effect by the proposed scheme is addressed.