• E2M - 전기 전자와 첨단 소재
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• 제8권6호
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• pp.744-751
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• 1995

This paper describes a study on absorption properties of electromagnetic wave by the composition ratio of Ni-Zn ferrite. Ni-Zn ferrite was composed of 48-52mol% Fe$\_$2/O$\_$3/, 18-22mol% NiO and 26-34mol% ZnO. The sintering of the composition was carried out at 1200.deg. C for 2 hours. Through the experiments, it was found that the resonance phenomenon occured at low frequency range for high permeability and vice versa. In the case of the composition of 49mol% Fe$\_$2/O$\_$3/, 20mol% NiO and 31mol% ZnO, the bandwidth ranged from 0.35GHz to 0.95GHz with the absorption thickness of 10mm. Also, in the case of the composition 51mol% Fe$\_$2/O$\_$3/, 22mol% NiO and 27mol% ZnO, the bandwidth ranged from 0.48GHz to 1.2GHz with the absorption thickness of 6mm.

• 대한금속재료학회지
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• 제46권1호
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• pp.44-51
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• 2008

The effects of magnetic powder size on electromagnetic wave absorption characteristics in Fe-6.5Si-0.9Cr(wt%) alloy flakes/polymer composite sheets available for quasi-microwave band have been investigated. The composite sheet including small magnetic flakes with the size less than $26{\mu}m$ exhibited high power loss in the GHz frequency range as compared with the sheets having large alloy flakes of $45{\sim}75{\mu}m$. Moreover, both the complex permeability and the loss factor increased with the decrease in size of the alloy flakes. The large power loss of the sheets containing small magnetic flakes was attributed to the high complex permeability, especially their imaginary part. The high complex permeability of the sheets composed of small flakes was considered to be due to the highly thin shape of the flakes inducing low eddy-current loss.

• Journal of Astronomy and Space Sciences
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• 제39권2호
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• pp.35-42
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• 2022

During their respective missions, the spacecraft Voyager and Cassini measured several Saturn magnetosphere parameters at different radial distances. As a result of information gathered throughout the journey, Voyager 1 discovered hot and cold electron distribution components, number density, and energy in the 6-18 Rs range. Observations made by Voyager of intensity fluctuations in the 20-30 keV range show electrons are situated in the resonance spectrum's high energy tail. Plasma waves in the magnetosphere can be used to locate Saturn's inner magnetosphere's plasma clusters, which are controlled by Saturn's spin. Electromagnetic electron cyclotron (EMEC) wave ring distribution function has been investigated. Kinetic and linear approaches have been used to study electromagnetic cyclotron (EMEC) wave propagation. EMEC waves' stability can be assessed by analyzing the dispersion relation's effect on the ring distribution function. The primary goal of this study is to determine the impact of the magnetosphere parameters which is observed by Cassini. The magnetosphere of Saturn has also been observed. When the plasma parameters are increased as the distribution index, the growth/damping rate increases until the magnetic field model affects the magnetic field at equator, as can be seen in the graphs. We discuss the outputs of our model in the context of measurements made in situ by the Cassini spacecraft.

• 한국전자파학회논문지
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• 제8권3호
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• pp.254-263
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• 1997

通信 및 電子훌業의 發達에 따라, 電磁波放射에 對한 밟素鐵維彈化樹(CFRTP)의 電磁波 避廠效果(SE)를 冊究하는 것은 重要하다. 本R究에서는 밟素熾維(CF)의 避빼옷效果를 電波8홉室內에서, 驗的으로 測定하였다. 使用한 樹服는 PC, PP, PEl, PMMA 및 PA이다. 實嚴은 分光分析器에 의해 鋼避蘇箱子와 모노폴안테나를 使用해 修行하였다. 훌훌結果로부터 CF는 良好한 電磁波適嚴材의 한 候補임을 알 수 있었다. SE는 CF의 積層의 增加에 따라 增加하였다. 徵小한 揚傷의 增加는 CF의 平面密度, 透過두께 및 反射角의 增加로 인해 SE를 增加 시켰다. SE에 미치는 다른 特性들은 母材樹服, 안테나問의 距離 및 노이즈의 周波數에 따라 달랐다.

• 한국전자파학회논문지
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• 제25권5호
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• pp.526-531
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• 2014

차량통신은 통신시스템과 차량산업을 융합하여 ITS(Intelligent Transport Systems) 분야에서 다양한 서비스 제공을 위해 고려되어 왔다. 일반적으로 차량통신은 WAVE(Wireless Access in Vehicular Environments)라고 알려져 있는 IEEE 802.11p/1609표준을 채택하여 vehicle-to-vehicle(V2V)와 vehicle-to-infra(V2I) 통신에 이용된다. WAVE 시스템은 OFDM(Orthogonal Frequency Division Multiplexing) 신호를 5.835~5.925 GHz대의 주파수를 사용하여 전송하는 시스템이다. 본 논문에서는 IEEE 802.11p 표준에 따라 구현한 WAVE 시스템의 MAC(Media Access Control)단에서 채널 모니터링을 32 비트 처리한 다음 데이터를 수신하여 성능을 평가하였다. 실제 고속도로에서 OBU(On Board Unit)로 구성된 테스트베드를 구축하고, OBU간에 WSM(WAVE Short Message)을 무선으로 송수신한 다음, 프레임 당 채널 점유 시간과 처리량을 산출하였다.

• 한국음향학회지
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• 제24권5호
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• pp.271-281
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• 2005

솔레노이드 코일을 이용하여 체외 충격파 치료술에 적합한 전자기식 충격파 발생기를 구성하였다. 충격파 발생기의 충격파의 특성은 바늘형 하이드로폰을 이용하여 평가하였다 충격파 발생기 방전 전압이 8에서 18 kV로 증가할 때 측정된 충격파의 최대 양압 (P+)은 $10\~77\;MPa$사이를 비선형적으로 증가하는 것으로 나타났다. 반면, 충격파 최대 음압 (P-)은 $-3.2\~-6.8\;MPa$ 에서 변화하고 있으며, 방전 전압이 14 kV에서 -6.9 MPa로 가장 낮은 값을 보였다. 동일한 설정에서 반복 측정된 충격파의 크기 P+는 평균값의 $5\;\%$ 이내에서 변화하며, 전기 수력학적 방식 충격파 발생기 경우의 $50\;\%$ 정도와 비교하여, 매우 작은 것으로 나타났다. 시간 축에서 1 ms 동안 측정한 하이드로폰 신호로부터 충격파에 의해 야기된 음향 공동 현상, 즉, 기포의 파열 현상으로 발생된 다수의 순차적인 음향 임펄스를 관찰할 수 있었다. 웨이블렛 변환 기법을 이용하여, 충격파 강도와 밀접한 관련이 있는 것으로 알려진, 첫 번째와 두 번째 기포 파열 시간 지연을 정확히 측정하였다. 충격파 크기 P+가 10 에서 77 MPa로 증가할 때 측정된 기포 파열 지연 시간은 120부터 $700\;{\mu}s$ 로 거의 선형적으로 증가함을 관찰할 수 있었다.

• Journal of electromagnetic engineering and science
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• 제5권3호
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• pp.140-145
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• 2005

In this paper, an experimental investigation for return loss and a software-based prediction for interference level of single-packaged filtering antenna composed of dielectric waveguide filter and PCB(Printed Circuit Board) slot antenna in transceiver module have been carried out with several different feeding structures in millimeter-wave regime. The implementation and embedding method of the existing air-filled waveguide filters working at millimeter-wave frequency on general PCB substrate have been described. In a view of the implementation of each components, the dielectric waveguide embedded in PCB and LTCC(Low Temparature Co-fired Ceramic) substrates has employed the via fences as a replacement with side walls and common ground plane to prevent energy leakage. The characteristics of several prototypes of filtering antenna embedded in PCB substrate are considered by comparing the wideband and transmission characteristics as a function of bent angle of transmission line connecting two components. In addition, as an essential to the packaging of transceiver module working at millimeter-wave, miniaturization technology maintaining the performances of independent components and the important problems caused by integrating and connecting the different components in different layers are described in this paper.

• Journal of electromagnetic engineering and science
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• 제8권2호
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• pp.70-75
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• 2008

In this paper, the EM wave absorber was designed and fabricated for countermeasure against EMI from a ceiling of a tollgate in ETC system. We fabricated several samples in different composition ratios of MnZn-ferrite, Carbon, and CPE(Chlorinated Polyethylene). Absorption abilities were simulated in accordance with different thicknesses of the prepared absorbers and changed complex relative permittivity and permeability according to composition ratio. The optimized mixing ratio of MnZn-ferrite, Carbon, and CPE was found as 40:15:45 wt.% by experiments and simulation. Then the EM wave absorber was fabricated and tested using the simulated data. As a result, the developed EM wave absorber has the thickness of 3.3 mm and absorption ability was more than 20 dB in the case of normal incidence and more than 11 dB for the incident angle from 15 to 45 degrees at 5.8 GHz. Therefore, it was confirmed that the newly developed absorber can be used for ETC system.

• 한국전자파학회논문지
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• 제27권5호
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• pp.471-481
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• 2016

밀리미터파 대역에서 동작하는 안테나의 성능 측정을 위한 컴팩트 레인지 설계 및 실험 결과에 대해 소개한다. 전기적 거대 구조인 컴팩트 레인지의 포물면 반사판에 의해 형성되는 측정영역의 평면파를 해석하기 위하여 물리광학 기법을 적용하였다. 제작한 밀리미터파 컴팩트 레인지는 측정영역 전계 분포 실험과 고이득 안테나 측정을 통해 성능을 검증하였다. 동작 주파수 75~110 GHz에서 측정영역 직경 50 cm를 갖도록 설계한 컴팩트 레인지의 전력 균일성은 0.75 dB 이하로 측정되었다.

• 한국전자파학회지:전자파기술
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• 제24권2호
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• pp.15-22
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• 2013

Low-Temperature-cofired ceramics (LTCC) antenna packages have been extensively researched and utilized in recent years due to its excellent electrical properties and ease of implementing dense package integration topologies. This paper introduces some of the key research and development activities using LTCC packaging solutions for 60 GHz antennas at Samsung Electronics [1]. The LTCC 60 GHz antenna element topology is presented and its measured results are illustrated. However, despite its excellent performance, the high cost issues incurred with LTCC at millimeter wave (mmWave) frequencies for antenna packages remains one of the key impediments to mass market commercialization of mmWave antennas. To address this matter, for the first time to the author's best knowledge this paper alleviates the high cost of mmWave antenna packaging by devising a novel, broadband antenna package that is wholly based on low-cost, high volume FR4 Printed Circuit Board (PCB). The electrical properties of the FR4 substrate are first characterized to examine its feasibility at 60 GHz. Afterwards a compact multi-layer antenna package which exhibits more than 9 GHz measured bandwidth ($S_{11}{\leq}-10$ dB) from 57~66 GHz is devised. The measured normalized far-field radiation patterns and radiation efficiency are also presented and discussed.