• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.4
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• pp.241-246
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• 2018

In this study, we proposed a wideband frequency tunable metamaterial absorber using a switchable ground plane (SGP). We proposed two fire retardant or flame resistant 4 (FR4) substrate structures for the SGP. An SGP is placed at the middle layer, between the top pattern and the bottom ground plane. The SGP can either be made ground or reactive, by switching the PIN diode ON/OFF. As the frequency is determined by the substrate thickness, the frequency can be switched from the SGP. The proposed absorber is demonstrated by full-wave simulations and measurements. When the SGP is turned on, an absorptivity higher than 90% is achieved from 3.5 GHz to 11 GHz. When the SGP is turned off, an absorptivity higher than 90 % is achieved from 1.7 GHz to 5.2 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.10
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• pp.1136-1141
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• 2007

In this paper, we designed and fabricated EM wave absorbers using Sendust, $Al(OH)_3$ and CPE(Chlorinated Polyethylene). We compared the absorption properties of samples containing 0 wt.%, 3 wt.%, 5 wt.%, 7 wt.% of $Al(OH)_3$. The optimized composition ratio of $Al(OH)_3$ is 5 wt.%, and the absorption property curve just has the tendency to improve at 5 wt.% of $Al(OH)_3$. And we used this characteristics to design the double-layered EM wave absorber. The double-layered EM wave absorber has thickness of 2 mm and has absorption ability more than 18.5 dB at a wireless LAN frequency band using 2.4 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.11
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• pp.1224-1230
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• 2007

Recently, wireless LAN are often applied in home or office because of its various of convenience. Frequency rage of wireless LAN specified by IEEE 802.11a is at 5.2 GHz and IEEE 802.11b is 2.4 GHz. But in offices with wireless LAN devices, reflection of waves against walls, ceilings, floors and desks made of metal creates multipath problems that reduce communication speed and lose data. These problems can be solved by using EM wave absorber. In this paper, we designed and fabricated EM wave absorbers using MnZn-ferrite, sendust, carbon and CPE(Chlorinated Polyethylene). The EM wave absorber with the ratio of 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 and the EM wave absorber with the ratio of MnZn-ferrite : carbon : CPE=40 : 15 : 45 wt.% has thickness of 3.8 mm and absorption ability more than 23 dB at 5.2 GHz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.162-166
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• 2000

In this paper, we studied the relation between using amount of Ferrite and electromagnetic wave absorbing properties of ferrite-rubber composite. The variation of using amount of Ferrite have been 52 wt.% ~ 62 wt.%. As s result, it has been shown that the electromagnetic wave absorbing properties of ferrite-rubber composite are related to the using amount of Ferrite in composite. And, we can control electromagnetic wave absorbing properties of ferrite-rubber composite by the control of using amount of Ferrite.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2002.03a
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• pp.53-57
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• 2002

In this paper, we explain new EM(electromagnetic) wave absorber that mixed NC (Natural Ceramics) and Ferrite with NL(Natural Lacquer). At first, a mixed NC and Ferrite(NC : F = (0.1~30)wt% : (99.9~70)wt%) bum at 95$0^{\circ}C$~125$0^{\circ}C$. And then, it is comminuted and injected into NL((NC+F) . NL = (30~80)wt% (70~20)wt%), finally we made Ferrite-NL EM wave absorber. Generally, conventional labor Ferrite covers only 500 MHz to 10 GHz under tolerance limits of 2 to 6 dB in absorption, and Ferrite-NL is over 8 ~ 14 dB. However, NCFerrite-NL huts superior absorption ability. It is over 16 to 19 dB through 500 MHz to 10 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.10
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• pp.841-850
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• 2015

With the rapid progress of electronics and radio communication technology, human enjoys greater freedom in information communication. However, EMW(Electro-Magnetic Wave) environments have become more complicate and difficult to control. Thus, international organizations, such as the American National Standard Institution(ANSI), Federal Communications Commission(FCC), the Comite Internationale Special des Perturbations Radio Electrique(CISPR), etc, have provided standard for controlling the EM wave environments and for the countermeasure of the electromagnetic compatibility(EMC). In this paper, fabrication of the smart EMW absorber which has heat radiating function and high performance absorption abilities were suggested. Furthermore, we prospected future smart EMW absorbers. The designed smart EMW absorber is fabricated following process. Firstly, we applied high temperature heat treated to a mixture of Iron-oxide($Fe_2O_3$) and ceramics. Secondly, we applied low temperature heat treated to the mixture of heat treated material and a carbon material. Lastly, we made apertures on the absorber. The designed smart EM wave absorber has the absorption ability of more than 20 dB from 2 GHz to 2.45 GHz band, respectively. Thus, it is respected that these results can be applied as various EMC devices in electronic, communication, and controlling systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.1
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• pp.19-24
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• 2017

In this paper, we propose a textile metamaterial absorber that using screen printing technology. A unit cell of the proposed absorber is motivated from the commercial Chanel logo for wearable applications. The complex impedance of the designed unit cell is analyzed by full-wave simulation. To verify its performance, the proposed metamaterial absorber is fabricated where the silver conductive ink is screen printed on an ordinary textile. From experimental results, the absorptivity of the proposed absorber is around 93 % at 10.8 GHz under normal incidence.

• 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.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.30-31
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• 2003

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1993.11a
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• pp.56-57
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• 1993