A Study on the Design and Fabrication of an Electromagnetic Wave Absorber for the 94-GHz Band

김대훈,김동일,최창묵 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.4

In this research, an electromagnetic wave absorber was developed for the 94-GHz detecting radar system. The electromagnetic wave absorber was designed and fabricated by using carbon black and chlorinated polyethylene, the composition ratio of which was determined as 30:70 wt.% by experiments and inspection. The absorption ability of the electromagnetic wave absorber was simulated using a finite difference time domain method by changing the thickness of the electromagnetic wave absorber. Then, the electromagnetic wave absorber was fabricated based on the simulated design. As a result, the measured results agree well with the simulated ones, and the developed electromagnetic wave absorber with a thickness of 0.7 mm had the desired absorption ability of more than 14dB in the frequency range of the 94-GHz band.

A Simulation and Property Analysis according to Electromagnetic Wave Absorber Shape

권석훈,황현석,강현일 한국인터넷방송통신학회 2018 International Journal of Internet, Broadcasting an Vol.10 No.4

The property of magnetic field and properties of EMW(Electro Magnetic Wave) absorption with multi-shaped EMW absorber was simulated. As a magnetic field having high density was showed at bottom of EMW absorber, simulation showed that overall EMW was absorbed at the bottom of multi-shaped absorber. The absorption properties of EMW according to thickness of absorber showed that it enhanced about 50-60 percent. Also, EMW absorption properties was checked with surface area of EMW absorber. A cylinder-shaped EMW absorber exhibited good property among multi-shaped EMW absorber based on these result.

Effects of Sheet Thickness on the Electromagnetic Wave Absorbing Characterization of Li<SUB>0.375</SUB>Ni<SUB>0.375</SUB>Zn<SUB>0.25</SUB>-Ferrite Composite as a Radiation Absorbent Material

Chong-Chul An,Gil-Bong Jung,Kwan-Jun Jo,Young-Ho Yoon,Dong-Young Kim 한국전자파학회JEES 2016 Journal of Electromagnetic Engineering and Science Vol.16 No.3

This paper reports on a study of LiNiZn-ferrite composite as a radiation absorbent material (RAM). The electromagnetic (EM) wave absorbers are composed of an EM wave absorbing material and a polymeric binder. The surface morphology, chemical composition, weight percent of the ferrite composite of the toroid sample, magnetic properties, and return loss are investigated using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and network analyzer. For preparing the absorbing sheet, chlorinated polyethylene (CPE) is used as a polymeric binder. The EM wave absorption properties of the prepared samples were studied at 4 - 8 GHz. We can confirm the effects of the thickness of the samples for absorption properties. An absorption bandwidth of more than a 10-dB return loss shifts toward a lower frequency range along with an increase in the thickness of the absorber.

옻의 특징과 옻을 지지재로 사용한 전자파 흡수체의 두께에 따른 흡수 특성 분석

최동한(Dong Han Choi),김동일(Dong Il Kim),김기만(Ki Man Kim) 한국항해항만학회 2004 한국항해항만학회 학술대회논문집 Vol.1 No.-

고성능 복합형 전자파 흡수체를 개발하기 위해 종래에는 지지재로서 주로 Silicone 고무나 CPE가 사용되어왔다. 본 연구에서는 전통 공예에서 사용되어 오던 옻에 대한 특징을 분석하고 옻의 전자파 흡수능을 조사하고 이를 지지재로 사용하여 MnZn 페라이트와 배합하여 전자파 흡수체를 제작한 경우의 전자파 흡수능을 조사하고, 흡수체의 두께에 따른 흡수능을 조사하였다. 옻을 지지재로 한 MnZn 페라이트 복합형 전자파 흡수체는 CPE나 Silicone 고무줄 지지재로 한 전자파 흡수체에 비하여 우수한 전파흡수특성 나타내었으며, 옻을 지지재로 사용한 전파흡수체의 두께 변화에 따라 정합주파수와 전파흡수능이 변화함을 알았다. Generally, a silicone rubber and a chloride polyethylene(CPE) have been for the development of high-performance composite EM(ElectroMagnetic) wave absorbers. In this study, the EM wave absorption abilities for natural lacquer which is newly suggested in this study as a binder for composite EM wave absorbers were investigated to develop an improved EM wave absorbers. In addition, MnZn ferrite composite EM wave absorbers mixed with the natural lacquer were prepared and their absorption ability was also investigated. MnZn ferrite composite EM wave absorption characteristics in comparison with the conventional binder such as a silicone rubber and a chloride polyethylene(CPE). The matching frequency and the absorption ability of EM wave absorbers mixed with natural lacquer can be controled the change of the thickness of them.

Intra/Inter-decoupling 전자파 흡수능 측정용 차폐형 루프안테나 제작 및 특성 평가

이준식,김기현 한국물리학회 2014 새물리 Vol.64 No.2

In order to evaluate the near-field electromagnetic wave absorption properties, we fabricated shielded loop antennas based on the IEC 62333-2 standard and we estimated their characteristics by using and electromagnetic-field three-dimensional simulator (finite element method). The electromagnetic wave absorption of the fabricated shielded loop antennas was evaluated, and the antennas exhibited good signal linearity within ±3 dB in the range of 0.1 ~ 10 GHz. These experimented results agreed with the simulation result, with a ±20 dB loss at the center frequency of 1 GHz. Finally, we secured a base for the IEC standard electromagnetic absorption evaluation method by evaluating commercial electromagnetic absorbers based on the intra-decoupling and the inter-decoupling method. 전자파 흡수체의 근접장 전자파 흡수능 특성을 평가하기 위하여 IEC 62333-2 표준 평가법에 제안되어 있는 차폐형 루프안테나를 유한요소법을 적용한 3차원 전자계 해석프로그램을 이용하여 설계하고 제작하여 안테나의 특성을 평가하였다. 제작된 차폐형 루프 안테나는 0.1 ~ 10 GHz 영역에서 ±3 dB 이내의 신호 선형성과, 중심 주파수 1 GHz 기준으로 각각 ±20 dB의 손실 범위 내에 있으며 전산모사 결과와도 잘 일치하였으며 전자파 흡수능 측정에 사용 가능함을 검증하였다. 인터 디커플링 (Inter-decoupling) 및 인트라 디커플링 (Intra-decoupling)평가법을 기반으로 제작된 차폐형 루프 안테나를 이용하여 상용 전자파 흡수체의 전자파 흡수능을 평가함으로써 IEC 표준 전자파 흡수 특성 평가 기반을 확보하였다.

Design of Ultrawide Bandwidth Electromagnetic Wave Absorbers with Square Patch Frequency Selective Surfaces with Different Geometries

Tian Liu,김성수 대한금속·재료학회 2020 대한금속·재료학회지 Vol.58 No.5

A reliable and efficient numerical method is presented for the design of broadband absorbers, fabricated by layering two square patch-frequency selective surfaces (SP-FSS) with different geometries on a grounded dielectric substrate. The circuit parameters of the inductance and capacitance of the SP-FSS were retrieved using the strip wire conductor model. Due to the high capacitance and low inductance of the SPFSS, a nearly constant resonance frequency (f0 = 37 GHz) is observed, irrespective of patch size at a given unit cell periodicity of 7.5 mm. For the SP-FSS, the circuit is capacitive below f0 and inductive above f0. For a grounded substrate with a quarter wavelength thickness, however, the input impedance is inductive below f0, resulting in impedance matching over a wide frequency range, with the controlled FSS resistance matched to the free-space impedance. The double-layer absorber was designed by optimizing the surface resistance and layer thickness of two SP-FSSs with different geometries, and demonstrated a 10 dB absorption bandwidth of 6.1−41.4 GHz with a total thickness of 5 mm, which is equal to the theoretical limit. A test sample was prepared by screen printing method, and the free space measurement demonstrated a wide-bandwidth absorption result (4.7−40.0 GHz for −10 dB reflection loss) with a small total thickness (5.4 mm). The simulation and experimental results strongly validated the SP-FSS for the design of wide bandwidth electromagnetic wave absorbers.

입도에 따른 Flake Sendust 전파 흡수체의 특성 분석

박수훈(Soo Hoon Park),김동일(Dong Il Kim),최동한(Dong Han Choi),김성연(Seong Yeon Kim) 한국전자파학회 2008 한국전자파학회논문지 Vol.19 No.9

본 논문에서는 연자성 금속 분말인 sendust를 flake화 과정을 통하여 형상과 입도를 변화시켜 전파 흡수체를 제작하고, 그 특성을 분석하였다. 먼저 attrition milling에 의해 입도를 달리한 세 종류의 flake sendust 분말과 지지재인 CPE(Chlorinated Polyethylene)를 이용하여 전파 흡수체를 제작하고, 이 전파 흡수체로부터 재료 정수를 계산하여 입도에 따른 변화를 조사한 후 전파 흡수능을 측정하여 비교ㆍ분석하였다. 그 결과 평균 입도가 140 ㎛ 인 flake sendust 분말로 제작된 전파 흡수체가 와전류 손실의 감소(복소비 투자율 증가)와 입자간의 정전 용량의 증가(복소비 유전율 증가)에 기인하여 고주파 대역에서 우수한 전파 흡수능을 보임을 확인하였다. In this paper, we analyzed the characteristics of the EM wave absorber which was fabricated by using Flake Sendust (soft metal magnetic powder). The Flake Sendust was made of 3 different granularity by attrition mill. First, we have fabricated 3 kind of EM wave absorbers using the Flake Sendust and CPE(Chlorinated Polyethylene) and measured the S-parameters of the EM wave absorber. The complex relative permittivity and permeability were calculated from the measured data and the variations according to a change of granularity were researched. As a result, it was confirmed that the EM wave absorber using flake Sendust with the 140 ㎛ average granularity has outstanding absorption ability in high frequency range(C band) for the reduction of eddy current loss(increase of permeability) and the increase of space charge polarization(increase of permittivity).

Epsilon Hard Ferrite Nanopowders for Millimeter Wave Absorption Application

표민지,최희락,백연경 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

Ferrites with excellent electrical and magnetic properties have widely used in various applications such as electronic inductors, magnetic recording tapes and microwave absorber. Among the ferrite family, epsilon iron oxide (ε-Fe₂O₃) has a giant coercive field (> 20 kOe) at room temperature, resulting in spectroscopic absorption in high frequency electromagnetic (EM) waves (30~300 GHz). However, it is difficult to synthesize high purity of ε-Fe₂O₃ for scale up via previous methods such as pulsed laser deposition and reverse-micelle & sol-gel method. Herein, we develop a facile aerosol approach to synthesize high purity ε-Fe₂O₃ nanopowder. The substitution of nonmagnetic elements to ε-Fe₂O₃ can be an effective method to tune coercivity, leading to the control of frequencies of EM waves to absorb. This strategy would pave the way for the mass production of millimeterwave absorber composed of ε-Fe₂O₃.

자기부상체 적용을 위한 전자파 흡수체의 특성 분석

서용범(Yong-beom Seo),강현일(Hyun-il Kang) 대한전기학회 2016 전기학회논문지 P Vol.65 No.1

EMC (Electro Magnetic Compatibility) of the electrical railway must be ensured for safety of passenger. Maglev trains has not friction between the wheels and the rails because levitation by an permanent magnets, electromagnets and superconducting magnets etc. So, it is advantageous to maintain a high speed without noise and vibrations. In this paper, we investigated that the magnetic field of the before and after installation electromagnetic waves absorber in order to analyze the effects of electromagnetic waves. The theoretical analysis of the electromagnetic wave absorber was simulated using finite element method. The magnetic field properties of electromagnetic waves absorber were measured by EMI (Electro Magnetic Interference) test receiver.

Synthesis of Gigantic Coercivity M-type Hexaferrites

조기련,표민지,손영국,백연경 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

Ferrites with excellent electrical and magnetic properties have widely used in industrial applications such as permanent magnets, microwave absorbers and magnetic memory media due to their low price and chemical stability. Among them, M-type hexaferrites (MFe₁₂O₁₉, M=Sr, Pb, Ba) with magnetoplumbite are known to have a high saturation magnetization of 70 emu/g and low coercive field (³⁺ ions with other suitable ions, such as Al³⁺, Cr³⁺, Ga³⁺, and replacing Sr²⁺ions with Ca²⁺ ions. Especially, M-type hexagonal ferrite substituted Al3+ ions for octahedral Fe3+ sites has very large coercivities, leading to lattice contraction of the unit cell. In this study, we synthesized hexaferrite particles (Sr_(1-x/12)Ca_(x/12)Fe_12-xAl_xO₁₉(x=4-6) with a coercivity over 20kOe via spray drying process. Thus, Sr-hexaferrite substituted with Al-Ca would be a good alternative for electromagnetic wave absorbers.