• Title/Summary/Keyword: 전파흡수체

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Design of the Broad-band EM Absorber Using the Improved Partial Initialization Genetic Algorithm (개선된 부분 초기화 유전자 앨거리즘을 이용한 광대역 전파흡수체 설계)

  • 이동근;남기진이상설
    • Proceedings of the IEEK Conference
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    • 1998.06a
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    • pp.161-164
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    • 1998
  • 광대역 주파수 상에서 외부로부터 입사하는 전자파를 산란시키지 않고 유전체 내부에서 흡수시키기 위해 유전체를 다층으로 배열하여 전파 흡수체를 최적 설계하고자 한다. 수직 및 여러 각도로 전파가 입사하는 경우 각 유전층의 두께, 유전 상수, 손실 탄젠트 등의 설계변수를 유전자 앨거리즘을 이용하여 최적화한다. 다극함수에서의 부분 초기화 유전자 앨거리즘의 성능 향상을 위해 부분 초기화율, 부분 초기화 시점, 스케일 인자의 변화에 따른 성능을 비교, 개선하여 흡수체 설계에 적용하였다.

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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.

Absorption Properties according to Particle Size of Ferrite in EM Wave Absorber for Mobile Phone (휴대전화용 전파흡수체에 있어서 페라이트 입자 크기의 제어에 따른 전파흡수특성)

  • 송재만;김동일;김수정;옥승민;김보영;박우근;이영구;윤현진;김기만
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.14 no.3
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    • pp.290-295
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    • 2003
  • In this study, we investigated the effect of particle size of Mn-Zn ferrite which is used as a material of electromagnetic wave absorber on electromagnetic wave properties. With increasing the particle size, the matching frequency is shifted toward lower frequency and the absorption ability of electromagnetic wave is decreased. We suggest that a sheet-type ferrite absorber composed of Mn-Zn ferrite with large particle is useful to compare with it composed of small particle size for mobile phone.

Analysis of Broad-Band Electromagnetic Wave Absorber for Single Polarized Wave by the Equivalent Material Method and the FDTD Method (등가재료정수법 및 FDTD법에 의한 단일편파용 광대역 전파흡수체의 해석)

  • 이수영;김동일;이종헌
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.9 no.3
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    • pp.296-304
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    • 1998
  • A design method of an electromagnetic wave absorber with ferrite fins in the second layer, which has very wide band frequency characteristics and is used for single-polarized wave absorption such as TV wave etc, has been designed. To examine the effectiveness of the Equivalent Material Constants Method$(EMCM)^{[1]}$ which is approximate method, the effective complex permittivity calculated by the Hashin-Strikman formulas and the EMCM are compared. Since, furthermore, the reflectivities by the EMCM in space and the FDTD method in an rectangular waveguide agreed well each other, it has been confirmed that the proposed electromagnetic wave absorber has excellent absorption characteristics in the frequency range of 30 MHz to 5830 MHz. Thus, it can be concluded that the EMCM is usefull to design and analyze the electro-magnetic wave absorber proposed here.

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Development of Composite Ba Ferrite EM Wave Absorbers for GHz Frequency (GHz 대역용 복합형 Ba 페라이트 전파흡수체의 개발)

  • 문상현;신승재;송재만;김동일;김기만
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.14 no.12
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    • pp.1329-1334
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    • 2003
  • We prepared EM wave absorbers by using recycled Ba ferrite far GHz frequency, and investigated the effects of carbon additions and preparation temperatures on their EM wave absorption properties. We clarified that it is very important to consider carbon amounts in Ba ferrite and preparation temperature for Ba ferrite EM wave absorbers with high quality.

A Study on the Evaluation of the Characteristics of Semi-Anechoic Chamber Constructed by the Cross-Shaped Type Electromagnetic Absorbers (십자돌기형 전파흡수체로 구성된 전파암실의 특성평가)

  • 김민석;김동일;전상엽;민경식
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.3 no.1
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    • pp.51-58
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    • 1999
  • In this Paper, the Performance of the semi-anechoic chamber which is to be constructed by the cross-shaped ferrite absorbers with broadband frequency characteristics, has been evaluated by the image method. As a result it was confirmed that the cross-shaped absorber has excellent performance over the frequency range from 30 MHz to 3,000 MHz, while the tile and the gird-type ferrite absorbers have the bandwidth of 30 - 1,000 MHz.

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A Study on Development of Electro Magnetic Wave Absorbers for Mobile Phones (휴대전화 단말기용 전파 흡수체의 개발에 관한 연구)

  • Choi Yun-Seok;Jung Jae-Hyun;Kim Dong-Il
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.17 no.5 s.108
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    • pp.423-429
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    • 2006
  • This paper deals with research for development of electromagnetic wave absorbers in sheet type for mobile phones. By controlling the sendust ratio, the $Al(OH)_3$ coating, the thickness, the kind of binders, and the milling time, electromagnetic wave absorbers were prepared and examined. Central frequency shills toward lower 2.2 GHz, 1.29 GHz, 842 MHz with increasing thickness 1 mm, 2 mm, 3 mm of the absorber, and absorption ability controlled each 2.2 GHz to 1.91 GHz, 1.29 GHz to 801 MHz, 842 MH2 to 801 MHz adjust sendust amount from 80 wt% to 85 wt%. The absorption band of the electromagnetic wave absorber coated with $Al(OH)_3$ becomes larger than that of non-coated one. Sendust composite microwave absorbers mixed with CPE were prepared at $70^{\circ}C$ in temperature. The fabricated electromagnetic wave absorbers show a reflection coefficient 5.76 dB at 1.8 GHz in thickness of 0.85 mm.

Microwave Absorption Properties in Composite Microwave Absorberby Control of Preparing Temperature (복합형 전파흡수체에 있어 시편제작 온도에 따른 전파흡수 특성)

  • 송재만;김동일;김수정;옥승민;문상현;신승재
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2003.05a
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    • pp.97-101
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    • 2003
  • Mn-Zn ferrite microwave absorbers mixed with silicon for mobile phone were prepared and the effect of preparation temperature of specimens on absorption ability was studied. A sample with the thickness of 1 mm prepared at 70 $^{\circ}C$ showed excellent absorption ability of 3.4 ㏈ at 1.8 GHz which is a frequency band for mobile phone. A loss factor of tan $\delta$ > 1 is shifted toward lower frequency as increasing preparation temperature of specimens.

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Development of the EM Wave Absorber Using MnZn-Ferrite and Sendust for Wireless LAN at 2.4 GHz (MnZn-Ferrite와 Sendust를 이용한 2.4 GHz 무선LAN용 전파흡수체 개발)

  • Lee, Dae-Hee;Choi, Chang-Mook;Choi, Dong-Han;Kim, Dong-Il
    • Journal of Navigation and Port Research
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    • v.31 no.10
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    • pp.865-868
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    • 2007
  • Recently, wireless LANs are often applied in home or office because of its various of convenience. Frequency range of wireless LANs specified by IEEE 802.11b is at 2.4 GHz. The bluetooth, the microwave oven, and the PDA(Personal Digital Assistants) uses, however, the same frequency band. So problems will be produced in these environments, such as multi-pass interference and system-to-system interference. These problems can be eliminated by using EM wave absorber. In this paper, we designed and fabricated EM wave absorber using MnZn-Ferrite, Sendust, and CPE( Chlorinated Polyethylene). The EM wave absorber with the ratio of material (MnZn-Ferrite : Sendust : CPE = 64 : 16 : 20 wt.%) has thickness of 3.7 mm and absorption ability more than 17 dB at 2.4 GHz.

A Study on the EM Wave Absorption Characteristics of Amorphous Metal Powder and Sendust Absorbers for RFID System (RFID 시스템용 Amorphous Metal Powder 및 Sendust 흡수체의 전파흡수 특성 연구)

  • Choi, Dong-Soo;Yoo, Gun-Suk;Choi, Dong-Han;Kim, Dong-Il
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2010.04a
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    • pp.159-160
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    • 2010
  • In this paper, we compared the absorption abilities of AMP and Sendust EM wave absorbers for a port logistics RFID system. Firstly, we fabricated EM wave absorber samples by using each absorbing material, AMP or Sendust, and CPE (Chlorinated Polyethylene) with composition ratios 85 : 15 wt. %. Secondly, we designed the optimum EM wave absorber using the calculated material constants found from the measured input impedance of the samples. Therefore, we confirmed that imaginary factor of complex relative permeability influences absorption ability and that AMP is better absorbing material than Sendust at the frequency band of 433 MHz.

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