• Title/Summary/Keyword: 전파흡수체

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Study of the Effects of Fe94Si5Cr1-Rubber Absorbers with Sheet-Thickness (Fe94Si5Cr1을 이용한 Sheet 두께에 따른 전파흡수특성 연구)

  • Kim, Moon-Suk;Min, Eui-Hong;Koh, Jae-Gui
    • Journal of the Korean Magnetics Society
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    • v.19 no.2
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    • pp.62-66
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    • 2009
  • The soft magnetic FeSiCr were processed the ball-mill for 30 hours and the shape of FeSiCr particles was changed from sphere to flake type, which was observed using scanning electron microscope. The complex permittivity and permeability spectra and reflection loss of FeSiCr-rubber composite was measured using Network Analyzer in order to investigate the relationship between the microwave absorption and the material constants. The matching frequency shifted toward lower frequency range with microwave absorber thickness, and microwave absorber with FeSiCr-rubber composite showed a maxium reflection loss of -8.3 dB at 1.86 GHz for a 1.3 mm thickness.

Development of the EM Wave Absorber for the Hi-pass Using Amorphous Powder (비정질 재료를 이용한 Hi-pass용 전파흡수체 개발)

  • Yoo, Gun-Suk;Kim, Dong-Il;Choi, Dong-Soo
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.20 no.6
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    • pp.562-569
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    • 2009
  • Recently, Hi-pass system(non-stop electric toll collection) using DSRC is working. However, it has various problems such as system errors by EM wave interference or multi-path reflection. The EM wave absorber is able to solve these problems. In this paper, we designed and fabricated EM wave absorber using amorphous substance. As a result EM wave absorber with composition of amorphous metal powder:CPE=45:55 wt.% has the thickness of 2.65 mm and absorption ability was higher than 40 dB at 5.8 GHz.

Numerical Computation of Matching Boundary Values of Electromagnetic Wave Absorbers (전파흡수체 정합경계값의 수치계산)

  • 김왕성;김경용;배규식
    • The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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    • v.6 no.2
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    • pp.19-26
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    • 1995
  • The design of broad-band, thin layer electromagnetic wave absorbers usually employs magnetic materials. The common absorber consists of a magnetic material layer bonded to a metal plate at the back. For such structure, a theoretical expression involving six parameters defines the allowable material shape and values of electromagnetic parameters that will produce zero reflection or more practically more than 99% absorption (20dB attenuation). The Secant Method was employed to compute the matching boundary values corresponding to 20dB attenuation. In addition, a search algorithm coupled with the Secant Method was developed to obtain allowable range of material parameters for the design of wave absorbers. These numerical methodes applicable to any six parameters effectively yielded accurate solutions in the least iterations.

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A Study on the Microwave Absorber Properties of Ni-Cu-Zn Ferrites Composite (Ni-Cu-Zn Ferrite의 복합형 전파흡수체 특성 연구)

  • Min, Eui-Hong;Kim, Moon-Suk;Koh, Jae-Gui
    • Journal of the Korean Magnetics Society
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    • v.17 no.6
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    • pp.238-241
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    • 2007
  • Ni-Cu-Zn ferrites were prepared by the co-precipitation. Physical properties and Microwave absorbing properties were investigated in Ni-Cu-Zn ferrite for the aim of microwave absorbers. From the analysis of X-ray diffraction patterns, we can see that all the particles have only a single phase spinel structure. The loss factor was maximum at sintering temperature $1100^{\circ}C$. The initial permeability of sintered ferrite obtained was an average of 50. We found that the $(Ni_{0.7}Cu_{0.2}Zn_{0.1}O)_{1.02}(Fe_2O_3)_{0.98}$ can be used in ferrite rubber composite microwave absorber when sintering temperature at $1100^{\circ}C$.

A Study on Design and Fabrication of mm-Wave EM Absorber (밀리미터파 대역 전파흡수체의 설계 및 제작에 관한 연구)

  • Kim, Dae-Hun;Choi, Chang-Mook;Choi, Dong-Su;Kim, Dong-Il
    • Journal of Navigation and Port Research
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    • v.34 no.3
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    • pp.161-166
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    • 2010
  • The bandwidth of detecting radars used for military purpose is increasingly broadened, and recently, the frequency band of the detecting radars is expanding to millimeterwave bands of the millimeterwave bands of 35 GHz and 94 GHz. Since, especially, it is essential and important to fabricate and develop EM wave absorber with the absorption ability more than 10 dB in 94 GHz band, the EM wave absorber was manufactured based on the design method by FDTD simulation. As a result, the developed EM wave absorber with the composition ratio of Binder(CPE with additional materials) : Carbon = 70 : 30 wt.% has the thickness of 0.7 mm and the absorption ability more than 14 dB in the frequency range of 94 GHz.

Design and Properties of Ferrite Absorber Used in Anechoic Chamber (전파무향실용 페라이트 흡수체의 설계 및 특성)

  • 한대희;김진석;오길남;조성백;김성수
    • The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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    • v.5 no.4
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    • pp.40-46
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    • 1994
  • Design and microwave absorbing properties of ferrite plate are investigated for the application to the radiowave absorbers used in anechoic chamber. The required frequency-dependence of complex permeability is determined on the basis of wave-impedance-matching relationship. The plate thickness and matchingfrequency are determined from the complex permeability and dielectric constant, and then compared with the directly measured reflection loss. A systematic variation of material constants and their influence on the microwave absorbing properties are demonstrated.

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Development of EM Wave Absorber for Increasing Communication Range in RFID System (RFID 시스템의 통신 거리 증대를 위한 전파흡수체 개발)

  • Park, Soo-Hoon;Kim, Dong-Il;Yoon, Sang-Gil;Yoo, Gun-Suk;Jeong, In-Seong
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.20 no.3
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    • pp.222-229
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    • 2009
  • In this paper, we designed and fabricated the EM wave absorbers for preventing the reduction of the communication range when RFID Tag is approached to a metal plate. The EM wave absorber samples were fabricated with difference composition ratios of Amorphous metal powder and CPE, the absorption abilities of which were simulated by substituting different thicknesses of the EM wave absorbers. Then the EM wave absorbers are manufactured based on the simulated results. By using the EM wave absorbers, we have confirmed the improvement effect of RFID tag antenna and the increase of communication range of RFID system. As a result, it was cleary shown that the communication range of RFID system is improved by adopting the EM wave absorber with the composition ratio of Amorphous metal powder:CPE=80:20 wt.% and the thickness of 4 mm. Thus, it was confirmed that the proposed EM wave absorber can increase the communication range of RFID system from 0.8 m to 5.2 m in UHF band.

A Study on EM Wave Absorber for Electromagnetic Wave Environment of Wireless LAN at 5.2 GHz (5.2 GHz 무선 LAN의 전자파 환경 대책용 전파흡수체에 관한 연구)

  • Yoo, Gun-Suk;Choi, Dong-Soo;Kim, Dong-Il
    • Journal of Navigation and Port Research
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    • v.34 no.1
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    • pp.15-19
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    • 2010
  • Recently, the wireless LAN system is rapidly growing because of its convenience of high speed communication. However, the wireless LAN systems at indoor places occur multi-propagation path by reflected waves from walls, ceilings, floors, and desks. Multipath problems cause transmission errors and degradation of communication speed. These problems can be solved by using EM wave absorbers. In this paper, we analyzed property of Graphite and derived the optimum ratio of Graphite: CPE to develop EM wave absorber for the wireless LAN system. First, we fabricated several samples in different composition ratios of Graphite and CPE, and then measured the reflection coefficient of each samples. Material constants of permittivity and permeability were calculated using the measured data and designed EM wave absorber. Secondly, the EM wave absorber was fabricated and tested on the base of the simulation data. As a result, it showed that the EM wave absorber in 1.7 mm thickness with the ratio of Graphite: CPE=50:50 wt.% has excellent absorption ability more than 27 dB at 5.2 GHz.

Development of Composite Sr Ferrite EM Wave Absorbers for GHz Frequency (GHz 대역용 복합형 Sr 페라이트 전파 흡수체의 개발)

  • Kim, Dong-Il;Moon, Sang-Hyun;Shin, Sung-Jae;Song, Jae-Man;Kim, Ki-Man
    • Journal of Navigation and Port Research
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    • v.28 no.6
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    • pp.503-507
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    • 2004
  • We prepared EM wave absorbers by using recycled Sr ferrite for GHz frequency, and investigated the effects of carbon additions and preparation temperatures on their EM wave absorption properties. A Sr ferrite EM wave absorber with the ratio of Sr ferrite: silicon rubber: carbon = 80 : 13.6: 6.4 wt% prepared at 7$0^{\circ}C$ showed -24 dB at 9.4 GHz and -23 dB at 5.5 GHz for 2 mm and 3 mm thickness, respectively.