• Journal of the Korean Society of Safety
• /
• v.19 no.2
• /
• pp.34-40
• /
• 2004

This paper presents an analysis of SAR(Specific Absorption Rate) distribution characteristics in a head model using FDTD(Finite Difference Time Domain). In this study human head was modelled in four elements-layered structure, consisting of skin, fat, skull and brain. To calculate the electromagnetic fields wihtin the head model, FDTD method was used. In the FDTD method, the electromagnetic wave is analyzed by solving a Maxwell's equations repeatedly. For the calculation, distance between power source and head model increased by 10[m]. Power density and incident electric field intensity were calculated. Based on the incident electric field, the program which calaculated internal electric fields intensity and SAR calculation of the head model were developed. The results of developed program using FDTD were compared with those of a commericial programs, which showed the availability and usefulness of the suggested scheme in this paper.

• Journal of electromagnetic engineering and science
• /
• v.13 no.1
• /
• pp.1-7
• /
• 2013

This paper proposes a metamaterial (MTM) absorber for 2.45 GHz band applications. The unit cell of the proposed absorber consists of an electric LC (ELC) resonator and a strip line, which are printed on opposite sides of the substrate. The ELC resonator comprises two split ring resonators (SRRs) and a connecting line with a resistor. The designed absorber exhibits an absorption of 94 % and a half-max bandwidth of 0.16 GHz at 2.45 GHz.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.1570_1571
• /
• 2009

본 논문에서는 초고주파를 이용하여 하지정맥류(Varicose vein)의 초기증상인 모세혈관 확장증(Telangiectasia)을 치료하는 데에 목적을 두었다. 유전율 차이에 따라 전자파(Electromagnetic waves)를 흡수하는 양이 다르다는 것을 전제하에 다리 모델링에 필요한 피부, 혈관, 혈액, 피하조직의 유전율을 구하였고, 혈관과 피부의 유전율에 비해 혈액의 유전율이 높다는 것을 통해 다른 조직에 비해 혈액의 전자파 흡수율이 높다는 것을 확인하였다. 피부의 구조와 유전율을 이용하여 모델링 한 후, 시뮬레이션을 통해 SAR(Specific Absorption rate)분포를 확인하였다.

• Journal of Electrical Engineering and Technology
• /
• v.12 no.4
• /
• pp.1634-1640
• /
• 2017

The purpose of this study is based on the electromagnet robot with a four-wheel drive which can climb up and down on structures of iron wall instead of human workers. Many of studies strive to develop wall riding-robots in terms of absorption system. However, the system needs additional devices too much to work out as well as electromagnetic wheel system also has much expense to make it. In this regard, this study makes efforts to find the way how to keep steady distance between wheel and wall while using general electromagnet to reduce motor load and to move robot so easily.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1993.11a
• /
• pp.71-74
• /
• 1993

In this paper, the permeability(${\mu}$$\sub$r′/, ${\mu}$$\sub$r"/), permittivity($\varepsilon$$\sub$r′/, $\varepsilon$$\sub$r"/) and absorption properties of Ferroxplana/Rubber composites were investigated. The composite specimens were prepared by molding and curing the mixtures of matrix rubber and Ni$_2$Y ferroxplana powders which were synthesized by coprecipitated method. The permeability(${\mu}$$\sub$r′/) of specimen was decreased in the range of 8∼12.5(GHz) and the permeability(${\mu}$$\sub$r"/) and Permittivity($\varepsilon$$\sub$r′/, $\varepsilon$$\sub$r"/) were increased. The optimum thickness of electromagnetic wave absorber (F/R=4, 1,200($^{\circ}C$) ), utilizing the Smith chart, was about 3.0(mm). The Figure of Merit was 93(%).

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2000.11a
• /
• pp.264-267
• /
• 2000

본 논문에서는 이동국의 안테나로부터 방사되는 전파의 일부가 인체에 흡수되므로써 기지국에서 수신되는 E$_{b}$ N$_{t}$의 감소에 대해 조사하였고, 감소된 E$_{b}$ N$_{t}$를 기준으로 하여 전파의 인체 흡수가 DS/CDMA BPSK 시스템의 성능에 미치는 영향을 분석하였다. 분석 결과, 인체에서의 흡수가 30[%]에서 40[%]로 증가할 때 기지국에서의 E$_{b}$ N$_{t}$, 값이 약 0.5 [dB] 정도 감소함을 알 수 있으며, 40 [%]에서 50[%]로 중가할 때에는 약 0.6 [dB] 정도 감소함을 알 수 있었다. 또한 시뮬레이션을 통해 사용자 수가 15 명일 때 약 2.5 [dB]의 E$_{b}$ N$_{t}$ 값에서 음성 서비스가 가능하다는 것을 알 수 있었다. 그리고 이러한 E$_{b}$ N$_{t}$ 값을 만족시키려면, 흡수율이 10 [%] 증가 할 때마다 안테나 방사 전력을 약 20 [mW] 이상 증가시켜야 한다는 것도 알아내었다. 것도 알아내었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.12
• /
• pp.1329-1334
• /
• 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.

• Journal of electromagnetic engineering and science
• /
• v.10 no.4
• /
• pp.206-211
• /
• 2010

In this paper, an implantable planar inverted-F antenna (PIFA) for an artificial cardiac pacemaker is proposed. The antenna has a simple structure with a low profile and is placed on the top side of the pacemaker. The dimensions of the pacemaker system, including the antenna element, are $42{\times}43.6{\times}11$ mm. When the antenna is embedded in pig tissue, its $S_{11}$ value is -10.94 dB at 403 MHz and the -10 dB impedance bandwidth of the antenna is 6 MHz (399~406 MHz). The proposed PIFA in tissue has a peak gain of -20.19 dBi and a radiation efficiency of 1.12 % at 403 MHz. When the proposed antenna is placed in a flat phantom, its specific absorption ratio (SAR) value is 0.038 W/kg (1 g tissue). Performances of the proposed PIFA is sufficient to operate at the MICS band (402 ~ 405 MHz).

• Journal of electromagnetic engineering and science
• /
• v.6 no.1
• /
• pp.71-75
• /
• 2006

In this study, EM wave absorbers based on Au coated conductive sheets were prepared, and their reflection and transmission coefficients were investigated. An Au coated conductive sheet showed the transmission loss higher than 40 dB in $1{\sim}18$ GHz. Ba ferrite EM wave absorbers with an Au coated conductive sheet showed enhanced EM wave absorption and shield to compare with Ba ferrite EM wave absorbers without conductive sheets. Proposed EM wave absorbers with conductive sheets are useful to protect EM machines from EM interference by strayfields.

• Journal of electromagnetic engineering and science
• /
• v.14 no.3
• /
• pp.314-316
• /
• 2014

This letter presents two types of metamaterial-inspired absorbers adopting resistive trumpet structures at the X band. The unit cell of the first type is composed of a trumpet-shaped resonator loading a chip resistor, a metallic back plane, and a FR4 (${\varepsilon}_r=4.4-j0.02$) substrate between them (single-layer). The absorption rate is 99.5% at 13.3 GHz. The full width at half maximum (FWHM) is 95 % at 11.2 GHz (from 5.9 to 16.5 GHz). The size of unit cell is $5.6{\times}5.6{\times}2.4mm^3$. The second type has been optimized with a $7{\Omega}$/square uniform resistive coating, removing the chip resistors but leading to results comparable to the first type. The proposed absorbers are almost insensitive to polarizations of incident waves due to symmetric geometry.