• Journal of Navigation and Port Research
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• v.30 no.8 s.114
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• pp.637-642
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• 2006

In this paper, we made an experiment on materials of two kinds. First, we made a study of Multi-layer EM wave absorbers using Sendust. In result, The bandwidth of the Multi-layer Sendust EM wave absorbers over 10 dB is extended in S-Band. Second, we investigated the mixing effects of AI(OH)3 on Multi-layer Sendust EM wave Absorbers. In result, the Multi-layer Sendust EM wave absorbers mixed with Al(OH)3 showed a extended bandwidth over 10 dB compared with non-mixed Multi-layer Sendust EM wave absorbers in S-Band.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.06b
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• pp.97-101
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• 2006

In this paper, Multi-layer EM wave absorbers using Sendust are presented. The bandwidth of the Multi-layer Sendust EM wave absorbers over 10 dB is extended in S-Band And we investigated the mixing effects of $Al(OH)_3$ on Multi-layer Sendust EM wave Absorbers. As a result, the Multi-layer Sendust EM wave absorbers mixed with $Al(OH)_3$ showed a extended bandwidth over 10 dB compared with non-mixed Multi-layer Sendust EM wave absorbers in S-Band.

• Proceedings of the Korean Magnestics Society Conference
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• 1994.03a
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• pp.90-91
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• 1994

• Electrical & Electronic Materials
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• v.9 no.1
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• pp.76-92
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• 1996

본 고에서는 대표적인 연자성재료인 Soft 페라이트, 퍼멀로이, 센더스트와 비정질 자성합금계의 특성과 용도를 살펴봄으로써 현재의 기술현황을 알아보고 그 문제점 해결과 특성개선을 위한 연구동향에 대하여 검토하여 보기로 한다. 또한 연자성재료 일반에 걸쳐 용도별 분류와 각 응용기술 분야에서의 기술동향 및 전망에 대하여 소개하고자 한다.

• Journal of the Korean Magnetics Society
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• v.4 no.2
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• pp.130-134
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• 1994

This paper describes the occurance of bumps in playback spectrum while reading with MIG heads. The amplitudes of the bumps in theoretically predicted frequencies are investigated by computer simulation. Three cases of MIG head structure are simulated, one without pseudo gaps, the other two with pseudo gap thicknesses of $0.02\;\mu\textrm{m}\;and\;0.2\;\mu\textrm{m}$ on both sides of the main gap, respectively. It is assumed that metal powder tapes are used. The results show that the bumps occur at predicted frequencies and the amplitudes of the bumps agree well with predicted values.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.3
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• pp.500-506
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• 2015

In this paper, we designed and fabricated the EM wave absorber consisted of Sendust for suppressing EM wave noise PCB in ISM (Industrial, Scientific and Medical) band of 2.4 GHz. We fabricated several samples with different composition ratios of some kinds of Sendust to CPE (Chlorinated Ploy-ethylene) as a binder, and it was confirmed that the optimum composition ratio of absorbing materials was Flaked Sendust : CPE = 72.5 : 27.5 wt.%.. The absorbing abilities were simulated by changing the thickness and the measured material constants of EM wave absorber. The measured absorption abilities were analyzed and compared with the simulated ones. As a result, the simulated results agree well with the measured ones, and the developed EM wave absorber with extremely thin thickness of 0.6 mm has absorption ability of 5.4 dB at 2.4 GHz is excellent one. The thin type EM wave absorber can be applied for suppressing and absorbing electromagnetic noises from information and communication equipments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1505-1510
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• 2014

High-Pass (ETC ; Electronic Toll Collection) system is one of the basic elements, which adopts a wireless communication method using 5.8 GHz and can realize a part of ITS (Intelligent Traffic System). On the other hand, communication errors occur frequently in Hi-Pass system due to signal erros, multi-path reflection, and/or system-to-system interferences. To solve these problems, an EM (Electro-Magnetic) wave absorber can be used. To solve these Problems, we fabricated some samples in the different composition ratios of Carbon, Sendust, and CPE, and it was confirmed that the optimum composition ratio of Carbon : Sendust : CPE is 10 : 40 : 50 wt.%. The complex relative permittivity and complex relative permeability were derived by using the measured data. In addition, the optimum design parameters for the absorber were determined by simulation. Then the absorption abilities were calculated by changing the thickness of the EM wave absorbers. As a result, the optimum thickness of the developed EM wave absorber was 2.85 mm with absorption ability over 22.4 dB at 5.8 GHz. Futhermore, the EM wave absorber was fabricated based on the simulated and designed values. The measured values agreed well with the simulated ones. Therefore, it was clearly shown that the developed EM wave absorber in this paper is to be applied in actual situations.

• Journal of the Korean Magnetics Society
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• v.14 no.1
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• pp.7-12
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• 2004

The annealing-temperature dependence of magnetic properties in compressed powder cores being composed of ball-milled F $e_{73.5}$C $u_1$N $b_3$S $i_{15.5}$ $B_{7}$ alloy powders (size 250∼850${\mu}{\textrm}{m}$) and 5 wt% of ceramic insulators has been investigated. When annealed at 5$50^{\circ}C$ for 1 h and so transformed to $\alpha$-Fe phase nanocrystalline structure with the grain size of 11 nm (electrical resistivity : 110 $\mu$Ω$.$cm), the highest effective permeability of 125 and quality factor of 53 were obtained, and the permeability persisted up to about 500 KHz. Further the core loss measured at the frequency of 50 KHz and the induction amplitude of 0.1 T was very low (230 mW/㎤). However the dc bias characteristics was not satisfactory as compared to that of conventional powder core materials(MPP, Sendust etc.). The inferior dc bias property of F $e_{73.5}$C $u_1$N $b_3$S $i_{15.5}$ $B_{7}$ alloy powder cores was attributed to the fact that the size of powder was too large for obtaining the same permeability with that of conventional materials.