• Title/Summary/Keyword: Electromagnetic absorber

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Design of Ferrite Electromagnetic Wave Absorber for Anechoic Chamber (전파무향실용 페라이트 전파흡수체의 설계)

  • 김동일;이창우;김하근;전상엽;정세모
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.3 no.1
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    • pp.43-50
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    • 1999
  • Electromagnetic wave absorbers for anechoic chamber are needed to broaden the useful frequency bandwidth, reduce the thickness, and decrease the weight. There are various absorbers proposed for the above conditions, but they could not decisively solve the above requirements. The Electromagnetic wave absorber made by a conventional ferrite tile has, for example, broadened the useful frequency bandwidth by the way of forming air layer. Therefore, an air layer is formed absorber between a reflection plate and a sintered Ni-Zn ferrite tile of 7 mm in thickness, which has reflectivity less than -20 dB from 30 MHz to 450 MHz in frequency band, far narrower than the aimed bandwidth. The purpose of this paper is on the development of a universal anechoic chamber for measuring radiated electromagnetic wave or immunity of electronic equipments, GTEM-cell, wall material for prevention of TV ghost, etc. Accordingly, in this paper, a broadened electromagnetic wave absorber is designed, which has the reflection characteristics less than -20 dB from 30 MHz to 5,430 or 8,000 MHz in the bandwidth. Then we will design a super broadband electromagnetic wave absorber by inserting square Ferrite Cylinders Type with the thickness less than 23.5 m in three-layed type and with the frequency band from 30 MHz to 5,430-8,000 MHz under the above tolerance limits.

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Electromagnetic Wave Absorber Sheet for 940 MHz Dedicated Short Range Communication Frequency Bands Using Fe Based Alloy Soft Magnetic Metal Powder (Fe-계 연자성 금속분말을 이용한 940 MHz 단거리 전용 통신 (DSRC) 대역 전파 흡수체)

  • Kim, ByeongCheol;Seo, ManCheol;Yun, Yeochun
    • Korean Journal of Materials Research
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    • v.29 no.6
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    • pp.363-370
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    • 2019
  • The recent development of information and communication technologies brings new changes to automobile traffic systems. The most typical example is the advancement of dedicated short range communication(DSRC). DSRC mainly consists of an intelligent transportation system(ITS), an electronic toll collection system(ETCS) and an advanced traveler information system(ATIS). These wireless communications often cause unnecessary electromagnetic waves, and these electromagnetic waves, in turn, cause frequent system malfunction. To solve this problem, an absorber of electromagnetic waves is suggested. In this research, various materials, such as powdered metal and iron oxides, are used to test the possibility for an effective absorption of the unnecessary electromagnetic waves. The various metal powders are made into a thin sheet form by compositing through processing. The electromagnetic characteristics(complex permittivity, complex permeability) of the fabricated sheet are measured. As a result, we achieve -6.5 dB at 940 MHz(77.6 % absorption rate) with a 1.0 mm-thickness electromagnet wave absorber, and -9.5 dB at 940 MHz(88.8 % absorption rate) with a 2.0 mm-thickness absorber.

Analysis of the Planar Electromagnetic Wave Absorber Using the Mode Matching Technique (모드정합법을 이용한 평면형 전자파 흡수체 해석)

  • Hur, Jun;Park, Jong-Eon;Choo, Hosung
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.30 no.4
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    • pp.270-274
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    • 2019
  • In this paper, we analyze a planar electromagnetic absorber by using the mode matching technique(MMT). The proposed electromagnetic absorber has a periodic structure composed of a perfect conductor and ferrite, and the transmitted and reflected powers in response to the incident wave with parallel polarization are calculated according to the thickness of the plate. The proposed absorber shows a high absorption compared to the cases of periodic slits with vacuum or the ferrite plate itself. The solution to the reflected and transmitted powers by MMT is also verified with the results from a commercial simulator.

A Simulation and Property Analysis according to Electromagnetic Wave Absorber Shape

  • Kwon, Seok Hun;Hwang, Hyun Suk;Kang, Hyunil
    • International Journal of Internet, Broadcasting and Communication
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    • v.10 no.4
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    • pp.1-5
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    • 2018
  • 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.

A Study on High Performance Electromagnetic Wave Absorber Using NC and Natural Lacquer Binder (NC와 옻칠을 소재로 한 고성능 전파흡수체에 관한 연구)

  • Kim, Dong-Il;Choi, Dong-Han;Park, Woo-Keun;Song, Jae-Man
    • Journal of Navigation and Port Research
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    • v.27 no.1
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    • pp.75-80
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    • 2003
  • The electromagnetic wave absorption ability of natural ceramics(NC), natural lacquer, and rubber was investigated. The natural ceramics showed absorption ability above 2.5dB at 2.5GHz~4.5GHz and natural lacquer showed better electromagnetic wave absorption ability than that of rubber. The simulation results of electromagnetic wave absorber ability in a absorber composed of natural lacquer and ferrite showed the reflection coefficient of -16dB at 0.5GHz~10GHz. It was shown that from the simulation results, the electromagnetic wave absorber composed of lacquer as a backing material have better absorption ability than that of the electromagnetic absorber composed of rubber.

Broad-Band Design of Ferrite One-body EM Wave Absorbers for an Anechoic Chamber

  • Kim, Dong-Il;Son, June-Young;Park, Woo-Keun;Park, Dong-Han
    • Journal of electromagnetic engineering and science
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    • v.4 no.2
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    • pp.51-55
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    • 2004
  • With the progress of the electronics industry and radio communication technology, certain problems, such as electromagnetic interference(EMI), have arisen due to the increased use of electromagnetic(EM) waves. International organizations such as CISPR, FCC, and ANSI have provided the standards for the EM wave environment and for the countermeasure of the electromagnetic compatibility(EMC). EM wave absorbers are used for constructing an anechoic chamber to test and measure EMI and electromagnetic susceptibility(EMS). In this paper, we have designed an one-body EM(electromagnetic) wave ferrite absorber, based on the equivalent material constants method for both normally and obliquely incident waves, whose absorption abilities are superior to that of the conventional ones. The fabricated absorber has a thickness of 27.68 mm and shows an absorption ability over 20 ㏈ in the frequency from 30 MHz to 6 ㎓.

A Study on Design of Broadband Electromagnetic Wave Absorber for Single Polarization (단일편파용 광대역 전파흡수체의 설계에 관한 연구)

  • 김동일;이수영;정세모
    • Journal of the Korean Institute of Navigation
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    • v.19 no.4
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    • pp.93-102
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    • 1995
  • A design method of an electromagnetic wave absorber with ferrite fins in the second layer, which has very wide band frequency characteristics, is proposed and discussed. A theoretical model using the equivalent material constants method is adopted, assessed for its accuracy by comparision with the Hashin-Shtrikman formulas and compared with the conventional absorbers. Based on the model, a wide band electromagnetic wave absorber with excellent reflectivity frequency characteristics in frequency range of 30MHZ to 3530MHZ has been designed.

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A Study on Composite EM Absorber's Absorption Characteristics Using Natural Lacquer by Binder (옻을 지지재로 사용한 복합형 전자파 흡수체의 흡수 특성에 관한 연구)

  • Choi, Dong-Han
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2003.11a
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    • pp.622-629
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    • 2003
  • Generally, a silicone rubber and a chloride polyethylene(CPE) have been used for the development of high-performance composite EM(ElectroMagnetic) wave absorber. 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 absorber were investigated to develop an improved EM wave absorber In addition, MnZn ferrite composite EM wave absorber mixed with the natural lacquer were prepared and their absorption ability was also investigated. MnZn ferrite composite EM wave absorber which employs the natural lacquer as a binder showed an improved 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 absorber mixed with natural lacquer can be controled the change of the thickness of them.

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A Design of Ferrite Electromagnetic Wave Absorber Three Layered Type with Wide-Band Characteristics. (광대역 특성을 갖는 3층형 페라이트 전파흡수체의 설계)

  • 이창우;김동일
    • Journal of the Korean Institute of Navigation
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    • v.22 no.4
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    • pp.51-57
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    • 1998
  • According to the rapid development of the electric industry, the demand of the frequency allocation and the usage of electromagnetic wave are increased due to automation of modem society. Electromagnetic wave absorbers for anechoic chamber are needed to broaden the effective frequency bandwidth, reduce the thickness, and decrease the weight. There are various absorbers proposed for the above conditions, but they could not decisively solve the above requirements. The Electromagnetic wave absorber made by a conventional ferrite tile has, for example, broadened the effective frequency bandwidth by the way of forming air layer(practically in urethane foam, etc.) on the ferrite tile. Therefore, an air layer is formed between a reflection plate and a sintered Ni-Zn ferrite tile of 7 mm in thickness, which has reflectivity less than -20 dB from 30 MHz to 400 MHz in bandwidth. In this paper, a broadband electromagnetic wave absorber are designed, which has the reflection characteristics less than -20 dB from 30 MHz to 8,000 MHz in the bandwidth. A super broadband electromagnetic wave absorber is achieved by inserting square Ferrite Cylinders Type with the thickness less than 23.5 mm and with the frequency band from 30 MHz to 8,000 MHz under the above tolerance limits. The purpose of this research is on the development of a universal anechoic chamber for measuring radiated electromagnetic wave or immunity of electronic equipments, GTEM-cell and also a wall material for preventing TV ghost, etc.

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Electromagnetic Wave Absorbing Properties of $Ni_{0.5}-A_{0.1}-Zn_{0.4}{\cdot}Fe_2O_4$ Ferrite-Rubber Composite with amounts of a Ferrite (Ferrite 함량변화에 대한 $Ni_{0.5}-A_{0.1}-Zn_{0.4}{\cdot}Fe_2O_4$ Ferrite-Rubber Composite의 전파흡수특성)

  • Park, Y.J.;Shin, K.H.;Heo, J.;SaGong, G.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.05a
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    • pp.45-49
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    • 2002
  • In this paper, we have studied about electromagnetic wave absorbing properties of ferrite-rubber composite with a variation of ferrite. Amounts of ferrite in a composite absorber were changed from 52 wt.% to 62 wt.%. As a result, it has been shown that the electromagnetic wave absorbing properties of ferrite-rubber composite are related to the amount of ferrite in composite absorber. As a summary, it could be controled the electromagnetic wave absorbing property of ferrite-rubber composite by changing some kinds of annex A and amount of ferrite.

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