• 한국정보통신학회논문지
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• 제3권1호
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• pp.35-42
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• 1999

This paper describes the characteristics of the complex isotropic ferrite-rubber composite for a super wideband electromagnetic absorber in RP-A-PF type, which can be used for an anechoic chamber, wall material to prevent TV ghost, etc. The $Ni_x-A_{0.1}-ZN_{(1-x0.1)}$. $Fe{_2}O_4$ ferrite powder has been fabricated. Using this, then, [$Ni_x-A_{0.1}-ZN_{(1-x0.1)}$. $Fe{_2}O_4$]-Rubber composite for RF-layer in the RF-A-PF type absorber has been fabricated and it's characteristics has been analyzed. As a result, it has been shown that the [$Ni_x-A_{0.1}-ZN_{(1-x0.1)}$. $Fe{_2}O_4$].Rubber composite has excellent electromagnetic wave absorbing properties.

• 자동차안전학회지
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• 제15권4호
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• pp.65-70
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• 2023

In the paper, we propose a design method and process of a hybrid V2X communication module that combines WAVE communication, LTE-V2X communication, and legacy LTE communication in evaluating vehicle V2X electromagnetic compatibility. C-ITS is suitable for safety service applications due to its low latency, and legacy LTE is suitable for applications such as traffic information and infotainment due to its high latency and high capacity. In order to evaluate the V2X communication system, the evaluation equipment must have communication performance of the same level or higher. The main design contents presented in this paper will be applied to the implementation of a hybrid V2X communication module for electromagnetic compatibility evaluation.

• 전자공학회논문지 IE
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• 제44권2호
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• pp.21-25
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• 2007

본 논문에서는 표면저항을 이용한 차폐성능 및 다층박막의 광학설계 후, roll- to-roll DC 스퍼터링 공정을 이용하여 PET(Polyethylene terephtalate) 필름위에 투명 전도성 산화물 박막인 ITO와 금속을 다층박막 구조(Multilayer)로 균질하게 증착한 전파차폐필름을 1m 넓이로 제작하고 광투과 및 전파차폐특성을 조사하였다. 각 층의 면저항 및 두께에 따라서 전자파 차폐성능과 광투과도를 최적화 할 수 있도록 설계되었고, 그 조건에 따라 필름을 제작하였다. 제작된 전파차폐필름은 2-18GHz 대역에서 99.5%의 차폐성능을 나타내었으며, 400-700 nm에서의 전광선 투과율은 83.1%로 우수한 시인성과 전파차폐특성을 보유하였다.

• 센서학회지
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• 제26권3호
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• pp.199-203
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• 2017

In this paper, we developed an underwater localization system for underwater robot docking using the electromagnetic wave attenuation model. Electromagnetic waves are generally known to be impossible to use in water environment. However, according to the conclusions of the previous studies on the attenuation characteristics in underwater, the attenuation pattern is uniform and its model was accurately proposed and verified in 3-dimensional space via the omnidirectional antenna. In this paper, a docking structure and localization sensor system are developed for a widely used cone type docking mechanism. First, we fabricated electromagnetic wave range sensor transmit modules. And a mobile sensor node is equipped with unmanned underwater vehicle(UUV)s. The mobile node senses the four different signal strength (RSS: Received Signal Strength) from fixed nodes, and the obtained RSS data are transformed to each distance information using the 3-Dimensional EM wave attenuation model. Then, the relative localization between the docking area and underwater robot can be achieved according to optimization algorithm. Finally, experimental results show the feasibility of the proposed localization system for the docking induction by comparing the errors in the actual position of the mobile node and the theoretical position through the model.

• 한국분말재료학회지
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• 제15권1호
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• pp.53-57
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• 2008

The amorphous $Fe_{73}Si_{16}B_7Nb_3Cu_1$(at%) alloy strip was pulverized using a jet mill and an attrition mill to get flake-shaped powder. The flake powder was mixed with dielectric $BaTiO_3$ powder and its dispersant to increase the permittivity. The powders covered with dielectric powders and its dispersant were mixed with a binder and a solvent and then tape-cast to form sheets. The absorbing properties of the sheets were measured to investigate the roles of the dielectric powder and its dispersant. The results showed that the addition of $BaTiO_3$ powders and its dispersant improved the absorbing properties of the sheets noticeably. The powder sheet mixed with 5 wt% of $BaTiO_3$ powder and 1 wt% of dispersant showed the best electromagnetic wave absorption rate because of the increase of the permittivity and the electrical resistance.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1993년도 추계학술대회 논문집
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• pp.144-148
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• 1993

This paper is a study on electromagnetic wave absorption properties for the composition ratio of Ni-Zn-Fe$_2$O$_4$. Li-Zn-Fe$_2$O$_4$was composed of Fe$_2$O$_3$ 48∼51mo1%, LiO 18 ∼22mo1%, ZnO 34∼27mo1%. and sintering was carried out at 1200$^{\circ}C$. Through the experiments, the resonance phenomenon occured at low frequence range for high permeability, and vice versa. Specialy, In the case of Fe$_2$O$_3$49mol%, NiO 20mo1%, ZnO 3lmol% ,and the matching thickness was 10mm , the absorbing bandwith was 0.35 ∼0.95GHz. Also, In the case of Fe$_2$O$_3$51mo1%. NiO 22mo1%, ZnO 27mol%, we could get the absorbing bandwith of 0.45∼1.2GHz when the matching thickness was 6mm. Therefore. it is proved that electromagnetic wave absorbers with the above bandwidth range can be fabricated successful1y.

• 한국군사과학기술학회지
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• 제1권1호
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• pp.114-127
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• 1998

A user friendly computer code(EMCOMST; Electro-Magnetic response for COMposite STructures) was developed which provides with computations of the response characteristics such as reflectance and transmittance to the incident wave angles, frequencies, composite thicknesses, ply orientations, and types of backplate as the linearly polarized transverse electro-magnetic wave is emitted to the advanced composite structures. In this investigation were reviewed the electromagnetic characteristics of the continuous orthotropic fiber-reinforced organic matrix composites with or without ferrite fillers, which are actively applied to low-weight and high-strength aircraft structures. Also were calculated the response of the three layered compound structures which have appropriately stacked above-mentioned materials as transmitting layer, absorbing layer, reflection layer, respectively under the specific thickness constraints for mechanical strength design requirements. For the composite structures presented in this study, minimum reflectance value less than -5㏈ can be obtained in the frequency range of 4 to 12 ㎓. In addition, analysis of structures attached isotropic radar absorbing materials(RAM) is facilitated by putting the material properties in the material input card entries adequately.

• Journal of Magnetics
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• 제14권4호
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• pp.155-160
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• 2009

This study examined the effects of a decrease in thickness of magnetic alloy flakes on the electromagnetic wave absorption characteristics of nanocrystalline $Fe_{73.5}Cu_1Nb_3Si_{15.5}B_7$ (at.%) alloy flakes/polymer composite sheets available for a quasi-microwave band. The thickness of FeCuNbSiB alloy flakes decreased to 1-2 $\mu$m with increasing milling time up to 24 h, and the composite sheet including alloy flakes milled for 24 h exhibited considerably enhanced power loss properties in the GHz range compared to the sheets having non-milled alloy powders. Although a considerable increase in loss factor upon milling was observed in the narrow frequency range of 4-6 GHz, there was no correlation between the complex permeability and flake thickness. However, the complex permittivity increased with increasing milling time, and there was good agreement between the milling time and the frequency dependences of the complex permittivity and power loss.

• 한국분말재료학회지
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• 제14권5호
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• pp.303-308
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• 2007

The oxidation of $Fe_{73}Si_{16}B_7Nb_3Cu_1$ nanocrystalline powder has been conducted to investigate its influence on the electromagnetic wave absorption characteristics of the soft magnetic material. Oxidation occurred primarily on the surface of nanocrystals. Oxidation reduced the real part of complex permeability due to the reduction of the relative volume of the powder, which otherwise contributes to the permeability. Oxidation reduced the absorption efficiency of the sheet at frequencies over 1GHz, indicating that the relative contribution of skin depth increments to the absorption was not significant. The pulverization and milling process lowered the optimum crystallization temperature of the material by $40{\sim}50^{\circ}C$ because of the internal energy accumulated during the fragmentation and powder thinning processes.

• ETRI Journal
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• 제41권6호
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• pp.731-738
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• 2019

We proposed a novel electromagnetic band-gap (EBG) cell-embedded antenna structure for reducing the interference that radiates at the antenna edge in wireless access in vehicular environment (WAVE) communication systems for vehicle-to-everything communications. To suppress the radiation of surface waves from the ground plane and vehicle, EBG cells were inserted between micropatch arrays. A simulation was also performed to determine the optimum EBG cell structure located above the ground plane in a conformal linear microstrip patch array antenna. The characteristics such as return loss, peak gain, and radiation patterns obtained using the fabricated EBG cell-embedded antenna were superior to those obtained without the EBG cells. A return loss of 35.14 dB, peak gain of 10.15 dBi at 80°, and improvement of 2.037 dB max at the field of view in the radiation beam patterns were obtained using the proposed WAVE antenna.