• Proceedings of the IEEK Conference
• /
• summer
• /
• pp.339-342
• /
• 2004

In this paper, we investigated methods to reduce SAR(Specific Absorption Rate) value with EMI(Electromagnetic Interference) paint distribution on front case of mobile handset. Simulations for several different EMI patterns were carried out. For the purpose of modeling, we used 3 dimensional CAD(Computer Aided Design) program, `Pro-engineering'. SAR simulation was done with SEMCAD, simulation platform for electromagnetic compatibility antenna design and dosimetry. In order to distinguish the individual pieces and to enable an assignment of the different material properties, each subfile was imported separately. In simulation, folding angle was set to $142^{\circ}.$ If we vary folding angle, different SAR value will be obtained. Among the tested EMI paint patterns, the hairpin pattern showed the best performance, i.e. the decrease efficiency of $16.5\%$ and horizontal-direction zigzag pattern showed the decrease efficiency of $12.2\%$ when we set the completely removed pattern as reference.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.4
• /
• pp.421-430
• /
• 2003

In this paper, we propose a method to consider SAR(Specific Absorption Rate) at beginning stage of handsets development. First, simulation was carried out with changing folding angle from 150$^{\circ}$to 142$^{\circ}$. Simulation results show that SAR value is decreased with decreasing the folding angle. When folding angle is 142$^{\circ}$, error between simulation and measurement results is about 3.95 %. Second, we made some experiments with EMI (Electromagnetic Interference) paint, and its results show that different pattern of EMI paint have different SAR values. After removing EMI paint at the lower part of antenna feeding point, we got the decrease efficiency of 15.46 % for SAR value. When we applied zigzag painting pattern, we got the highest SAR decrease efficiency.

• Journal of the Korean Society of Safety
• /
• v.19 no.4 s.68
• /
• pp.80-85
• /
• 2004

Electromagnetic interference(EMI) shielding characteristics of composite filled with Cu flake and carbon brush powder as hybrid conductive filler and EAF slag have been studied. The coaxial transmission line method of ASTM D4935-99 was used to measure the EMI Shielding effectiveness of composites as formulation in frequency rage $100\~1,000MHz$ The SE also increases with the increase in flier loading. The hybrid filler filled composites show higher SE compared to that of only Cu flake. The correlation between SE and conductivity of the various composites is also discussed. The results indicate that the composites having higher filler loading$({\geq}40wt.\%)$ can be used for the purpose of safety materials to protect hazardous electromagnetic interference.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2006.08a
• /
• pp.872-876
• /
• 2006

This study was made to examine the electromagnetic interference(EMI) shielding effect (SE) of multilayered thin films in which indium-tin oxide(ITO) and Ag were deposited alternately from 3layer to 9 layer on Poly Methyl Meth Acrylate(PMMA) substrate at room temperature using a PF sputtering. We measured optical and electrical characteristics by UV-spectrometer and 4 point probe. The measurement of EMI SE in frequency range from 50MHz to 1.5GHz was performed by using ASTM D4935-89 method. We compared the measured EMI SEs with theoretical simulation data. We obtained relatively low resistivity and high transmittance from the EMI SE multilayers. In this study, we obtain good optical electrical characteristics with a minimun transmittance of about 60% at 550nm wavelength and sheet resistance of $2{\sim}3ohm/sq$., respectivity. Measured EMI SEs were over 50dB and similar to theoretical simulation data.

• Smart Structures and Systems
• /
• v.25 no.3
• /
• pp.385-391
• /
• 2020

In this paper, a new passive lossless snubber circuit with energy transfer capability is proposed. The proposed lossless snubber circuit provides Zero-Current Switching (ZCS) condition for turn-on instants and Zero-Voltage Switching (ZVS) condition for turn-off instants. In addition, its diodes operate under soft switching condition. Therefore, no significant switching losses occur in the converter. Since the energy of the snubber circuit is transferred to the output, there are no significant conduction losses. The proposed snubber circuit can be applied on isolated and non-isolated converters. To verify the operation of the snubber circuit, a boost converter using the proposed snubber is implemented at 70W. Also, the measured conducted Efficiency Electromagnetic Interference (EMI) of the proposed boost converter and conventional ones are presented which show the effects of proposed snubber on EMI reduction. The experimental results confirm the presented theoretical analysis.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.9 s.100
• /
• pp.903-908
• /
• 2005

In this paper, in order to consider SAR(Specific Absorption Rate) problem at the beginning stage of a handset development, we investigated the Shh value change by using simulation method according to various EMI(Electromagnetic Interference) paint patterns on front case of a handset and folding angles. First, we made some experiments with EMI paint pattern on front case of a handset, and obtained results showed that different patterns of EMI paint had different SAR values. Among the simulation results on SAR value according to EMI paint patterns, the hairpin pattern showed the best performance, i.e. the decrease efficiency of $8.04\%$ and completely removed pattern showed the decrease efficiency of $5.94\%$. Orignal pattern was set as the reference and the folding angle was $150^{\circ}$. Second, simulation was carried out with changing folding angle from $150^{\circ}$ to $140^{\circ}$ and $160^{\circ}$. Simulation results for the modeled handset showed that SAR value was decreased with increasing the folding angle. When the folding angle was $160^{\circ}$ and with original pattern, we got the SAR value of about 1,61 W/kg. When we applied hairpin pattern with the folding angle of $160^{\circ}$, we got the lowest SAR value of about 1.45 W/kg.

• Applied Chemistry for Engineering
• /
• v.25 no.6
• /
• pp.613-618
• /
• 2014

In this study, nitrogen doped graphene oxide (GO) was prepared using liquid phase ammonia treatment to improve its electrical properties. Also, the aminated GO was manufactured into a film format and the electromagnetic interference (EMI) shielding efficiency was measured to evaluate its electrical properties. The XPS result showed that the increase of liquid phase ammonia treatment concentration led to the increased nitrogen functional group on the GO surface. The measurement of EMI shielding efficiency reveals that EMI shielding efficiency of the liquid phase ammonia treated GO was better than that of non-treated GO. When GO was treated using the ammonia solution of 21% concentration, the EMI shielding efficiency increased by -5 dB at higher than 2950 MHz. These results were maybe due to the fact that nitrogen functional groups on GO help to improve the absorbance of electromagnetic waves via facile electron transfer.

• Journal of Power Electronics
• /
• v.15 no.3
• /
• pp.602-609
• /
• 2015

In this paper, a zero current transition (ZCT) double-ended flyback converter is proposed. All of the switching elements act under soft switching conditions and the voltage stress of the main switches is limited to the input voltage due to the innate behavior of the double-ended flyback converter. Providing soft switching conditions and clamping the voltage stress improves the efficiency and electromagnetic compatibility (EMC). The Proposed converter is analyzed in detail and its operating modes are discussed in detail. Experimental results are presented to verify the theoretical predictions. Moreover, the conducted electromagnetic emissions of the proposed ZCT double-ended flyback converter are measured to show another merit of the proposed converter in addition to providing soft switching conditions. The measured electromagnetic interference (EMI) of the proposed converter demonstrates that its EMI is lower than the conventional double-ended flyback converter. Furthermore, two simple and cost effective EMI reduction methods are applied to satisfy the EMC standard.

• Carbon letters
• /
• v.12 no.1
• /
• pp.48-52
• /
• 2011

The conducting polymer-coated multi-walled carbon nanotubes (MWCNTs) were prepared by template polymerization of aniline and pyrrole on the surface of MWCNTs in order to develop the novel electromagnetic interference (EMI) shielding materials. The conducting polymer phases formed on the surface of MWCNTs were confirmed by field emission-scanning electron microscopy and field emission-transmission electron microscopy. Both permittivity and permeability were significantly improved for the conducting polymer-coated MWCNTs due to the intrinsic electrical properties of MWCNTs and the conducting properties of coated polymers. The electromagnetic waves were effectively absorbed based on the permittivity nature of conducting polymer and MWCNTs preventing the secondary interference from reflecting the electromagnetic waves. The highly improved EMI shielding efficiency was also obtained for the conducting polymer-coated MWCNTs showing the synergistic effects by combining MWCNTs and the conducting polymers.

• Journal of Powder Materials
• /
• v.31 no.1
• /
• pp.57-76
• /
• 2024

Recent advancements in electronic devices and wireless communication technologies, particularly the rise of 5G, have raised concerns about the escalating electromagnetic pollution and its potential adverse impacts on human health and electronics. As a result, the demand for effective electromagnetic interference (EMI) shielding materials has grown significantly. Traditional materials face limitations in providing optimal solutions owing to inadequacy and low performance due to small thickness. MXene-based composite materials have emerged as promising candidates in this context owing to their exceptional electrical properties, high conductivity, and superior EMI shielding efficiency across a broad frequency range. This review examines the recent developments and advantages of MXene-based composite materials in EMI shielding applications, emphasizing their potential to address the challenges posed by electromagnetic pollution and to foster advancements in modern electronics systems and vital technologies.