• Water for future
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• v.28 no.6
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• pp.183-191
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• 1995

Applying microwave, a velocity measurement system has been developed in order to measure the velocity of stream water surface. It's main purpose is the measurement for high velocity of flood water. It is under the developing stage of experimental measurement system. The microwave surface velocity meter uses Doppler effects of microwave. It consists of a radio frequency(RF) part and that of signal processing. Thr RF part has the function of microwave oscillation, reception of reflected wave, and determination of Doppler frequency, etc. Signal processing designates amplification, fast Fourier transform, etx. Various measuring experiments were performed at bridges and a spillway of Taechong re-regulation dam with the microwave velocity meter. Verification test was also made through water tank of ship model test at Research Institute of Ships and Ocean Engineering. It shows 4% error inherent in A/D converter and additional several percentage errors from measurement circumstance. The measuring ranges are from 0.5 to 3.5 m/s. The result shows good linear relationship between carriage velocity and measured velocity, thus proves usefulness as a measuring instrument for flood water velocity. The instrument requires overall re-engineering procedure and number of data should be accumulated and analyzed to treat wind effects and random fluctuations of water surface.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.2
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• pp.149-155
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• 2014

In this paper, we study the complex mobile antenna for WPT(Wireless Power Transfer) with NFC(Near Field Communication) of inductive coupling using FPCB which has half thickness compared with the existing coil type antennas. Considering the pattern thickness of loop antenna, the analysis of electromagnetic wave absorber and battery's influence, absorber thickness, the ranges of design parameters are obtained. The proposed antenna has 0.45 mm thickness using single layer 3 oz FPCB and absorber. From measurement, the characteristics of NFC antenna can be satisfied with the specifications of EMVCo. and domestic mobile telecommunication and the transmission efficiency of the proposed WPT antenna is 68.1 % which is competitive with the existing coil type antenna. From the results of this paper, it has been confirmed that the proposed antenna can be used as the WPT and NFC antenna for mobile phone. Key words: Wireless Power Transfer, Near Field Communication, Mobile Phone Antenna, Absorber, FPCB.

• Applied Chemistry for Engineering
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• v.25 no.3
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• pp.268-273
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• 2014

In this study, multi-walled carbon nanotubes (MWCNT) were treated with nickel by electroless plating method for improving electromagnetic interference (EMI) shielding performance of MWCNT. The physical properties of electroless plated MWCNT were analyzed by using ultra-high resolution scanning electron microscope (UHR-SEM), thermogravimetry (TGA), sheet resistance analyzer and EMI shielding analyzer. EMI shielding efficiencies of nickel electroless plated MWCNT were measured to be 16 dB from 800 MHz band, which was 1.6 times increased compared to that of the activated MWCNT. Also, the average sheet resistance of nickel electroless plated MWCNT was measured to be $70{\Omega}/sq$, which was 56% decreased compared to that of the activated MWCNT. This result could be attributed to the plating morphology on the surface of MWCNT. This result could be attributed to uniformity of plating morphology on the surface, which has more effect on EMI shielding efficiency than the amount of nickel plating.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.6
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• pp.824-832
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• 1998

The significant additional path loss is caused by scattering, diffraction, and attenuation of propagation. Most of the wave propagation models for rural areas mainly have considered the influence of topography but ignored the effects due to land usage. The goal of this paper is development of the field strength prediction program for Cheju which is used the contour map and the effects due to land usage. In oder to classify the propagation path and divide the environment of land, data of the terrain and the land-cover are formed into a pixel. Two-ray model is transformed into equivalent model by the predicted reflection coefficient and the slope of terrain. For non line of sight, the additional loss is determined by quantitative analysis. The result show good accord and the wave propagation model program can be applied to predicted the service region in rural area of Cheju.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.2 s.117
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• pp.219-226
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• 2007

In this paper, we report phase noise effects on SER(Symbol Error Rate) of MQAM(M-ary Quadrature Amplitude Modulation), DPSK(Differential Phase Shift Keying), OFDM(Orthogonal frequency Division Multiplex)-MQAM and OFDM-DPSK. SER of each modulation method has been quantified at the various offset frequencies of the local oscillator and compared with phase noise effects with the ideal cases, which have no phase noise, through the MATLAB simulation. And the ratio of modulation bandwidths to the SERs at the various frequency offsets for the above modulation methods have been analyzed for the system requirement of minimum phase noise characteristics.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.1
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• pp.62-69
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• 2014

In this paper, WBAN(Wireless Body Area Network) On-body system using the surface-oriented antenna about the impact of human internal organs were analyzed through experiments. The received signal strength is measured for effect of human using the human model and the phantom of torso. Experiments are performed in anechoic chamber without moving and measured by Vector Network Analyzer. This paper confirms the effect of human body by comparing the human model and the phantom of torso. And also know the human internal organs effect on the antennas loss of received signal strength by measured data.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.1
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• pp.108-113
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• 2014

This paper presents the influence on the transmission characteristics of swelling in rectangular waveguides for Q-band. We derived the Green's functions of the waveguide with eigenfunction expansion method. The reflection coefficient of the waveguide with a swelling is calculated by using internal impedance in order to investigate the influence of swelling in the waveguide. In order to check the validity of the theoretical analysis, the calculated reflection coefficients are compared with the measured results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.4
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• pp.600-610
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• 2001

The effects of group delay and non-linear characteristics on high data rate(HDR) satellite channel are presented in this paper Based on the modeling of group delay and non-linear characteristics the system performances which provide various data rate services were analyzed in Ka-band satellite channel. As the transmission data rate is increased, the degradation due to these channel characteristics is severely increased. The linear component of group delay and the AM-AM component of non-linear characteristics severely affect the system performance. To efficiently provide the various service via the same transmission system it is necessary to equalize the primary impairment factors. The optimum operating points of HDR satellite transmission system are implemented by considering the analyzed results on channel characteristics.

• ETRI Journal
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• v.14 no.4
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• pp.210-216
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• 1992

불요 전자파 제거용 필터의 유전체로 사용되는 Zirconium Titanate 세라믹 유전체에서 $MoO_2$ 함유량과 소결온도에 변화를 주어 이들이 유전특성에 미치는 영향에 대하여 검토하였다. 일반적으로 $MoO_2$ 함유량보다는 소결온도의 변화가 유전률, 품질계수 및 소결밀도 등에 더 큰 영향을 주었으며, 정전용량의 온도계수 측면에서는 $MoO_2$ 함유량을 제어하여0ppm$^\{circ}C$근처로 이동시켜 상당히 안정된 온도 특성으로 개선할 수 있었다.

• Progress in Medical Physics
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• v.8 no.1
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• pp.53-67
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• 1997

General hospitals have being under the influence of various and specific environment of electromagnetic field. The factors are development of medical electric equipment and device with enlarged functional demands, in high power and multi-frequency. It has all of both faces, EMI(electromagnetic interference) and EMS(electromagnetic susceptibility). In additional, expansion of personal communication system(cellular phone) has many unreliable factor of using time and area, making noise of electromagnetic fields. We studied actual conditions of EMI in the medical site, where is numerous medical equipment, especially central operation room and ICU(intensive care unit), AKR(artificial kidney room : hemo-dialysis unit), etc. The influence, most of medical equipments made electromagnetic nosie has various factors in its band of frequency, harmonics and strength. In the experimental use of electro-surgical unit and cellular phone, noticeable and considerable noise of eletromagnetic fields were measured. All of that can make trouble and errors on the steadiness of bioelectrical devices. In conclusion, It is necessary to reconsiderations of reallocating EMI source vs. EMS factor, and set to definite forbiding area of using cellular phone. For maintenance of steady normal conditions, in spite of existing any other legal standards of safty level, it need considering all of alternative electromagnetic situations on a case-by-case basis.