• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.12 s.103
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• pp.1222-1228
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• 2005

Analysis on the field uniformity inside of a reverberation chamber was done at 2.45 GHz which is an operating frequency of MWO(Microwave Oven). The Schroeder's Quadratic Residue Diffuser was designed for the chamber, and 3 different types of diffusers have been investigated using the finite-difference time-domain(FDTD) method for the field characteristics of each type. Type 2 and 3 diffusers were filled with dielectric material, and the size of these could be designed smaller than Type 1, without degradation of field characteristic. Type 3 diffuser shows better results among the three types of diffusers in view of increased test region and better field uniformity.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.1 s.104
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• pp.74-80
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• 2006

This paper presents the characteristics of electromagnetic field uniformity in a reverberation chamber that can be used alternatively for the analysis, test and evaluation of electromagnetic interference and immunity. The dual-band diffuser, which can be used at two different frequency bands in a reverberation chamber, is applied, and it is made of two different single-band Schroeder's Quadratic Residue Diffusers. The FDTD method is used to analyze the field characteristics. Compared with single-band diffuser, the dual-band diffuser shows the improvement in not only expansion of test frequency band but also in characteristics of the field uniformity, polarity, power efficiency, and tolerance. Therefore, the reverberation chamber with the dual-band diffuser is a better facility, for the analysis and measurement of electromagnetic interference and immunity, than the reverberation chamber with a single-band diffuser.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.2
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• pp.227-233
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• 2001

Electromagnetic field characteristics of Reverberation chamber, which could be applicable for an alternative test facility of electromagnetic interference and radiated electromagnetic susceptibility have been investigated. To obtain the required field uniformity of reverberation chamber, Schroeder method Quadratic Residue Diffuser was designed to be applied to chamber. In this paper, 3 different types of diffusers depending on diffuser's periodic direction have been used to investigate field characteristics of each type by using FDTD numerical method. The results show all 3 types of reverberation chambers have below $\pm$3 dB tolerance of field uniformity characteristics, and the symmetrical, type 3, structure show better results among them.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.4
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• pp.373-378
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• 2002

This paper presents the results of an electromagnetic field uniformity of a triangular reverberation chamber that can be used alternatively for analysis and measurement of electromagnetic interference and immunity test. Equilateral triangular reverberation chamber and Schroeder diffusers were designed and fabricated for this purpose. FDTD simulation method was applied to analyze the field distribution inside of two different types of reverberation chambers. As a result, the electromagnetic field uniformity was improved inside of triangular reverberation chambers, and the measured field uniformity was improved by 1 ∼4 ㏈ compared to the ones without diffusers.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.8
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• pp.121-127
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• 2008

This paper presents an electric field distribution in a reverberation chamber using cylindrical diffuser. The characteristics of electric field distributions are compared with QRD(Quadratic Residue Diffuser) and cylindrical diffuser for $1{\sim}3$ GHz frequency band. The FDTD(Finite-Difference Time-Domain) method is used to analyze the field characteristics, and the field uniformity. At 2 GHz, the standard deviation and the tolerance of test volume in the reverberation chamber are improved by 0.11 dB, 0.43 dB for the case of cylindrical diffuser. The field strength is increased by 43.2 dBmV/m vs QRD's of 36.6 dBmV/m. Comparing with QRD's, the characteristic of polarization is also improved. These results show that reverberation chamber using cylindrical diffuser can be used alternative facility for measurement of electromagnetic interference and immunity.

• Journal of Radiation Protection and Research
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• v.38 no.2
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• pp.60-67
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• 2013

A diffusion coefficient is an important parameter in the prediction of atmospheric dispersion using a Gaussian plume model, and its modelling approach varies. In this study, dispersion coefficients recommended by the U. S. Nuclear Regulatory Commission's (U. S. NRC's) regulatory guide and the Canadian Nuclear Safety Commission's (CNSC's) regulatory guide, and used in probabilistic accident consequence analysis codes MACCS and MACCS2 have been investigated. Based on the atmospheric dispersion model for a hypothetical accidental release recommended by the U. S. NRC, its influence to atmospheric dispersion factor was discussed. It was found that diffusion coefficients are basically predicted from a Pasquill- Gifford curve, but various curve fitting equations are recommended or used. A lateral dispersion coefficient is corrected with consideration for the additional spread due to plume meandering in all models, however its modelling approach showed a distinctive difference. Moreover, a vertical dispersion coefficient is corrected with consideration for the additional plume spread due to surface roughness in all models, except for the U. S. NRC's recommendation. For a specified surface roughness, the atmospheric dispersion factors showed differences up to approximately 4 times depending on the modelling approach of a dispersion coefficient. For the same model, the atmospheric dispersion factors showed differences by 2 to 3 times depending on surface roughness.

• Proceedings of the Korean Environmental Health Society Conference
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• 2005.11a
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• pp.106-109
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• 2005

확산형 시료 채취기와 직독식 기기(공정시험법, Nitrogen Oxides Analyzer Model; EC 9841, Ecotech, Australia)에 의한 $NO_2$, 농도를 비교하고, 능동시료채취기(공정시험법)와 확산형포집기에 의한 HCHO(포름알데히드) 농도를 비교하기 위해 서울 ${\cdot}$ 경기 또는 대전, 충남 ${\cdot}$ 북지역에 소재한 11개 시설(종합병원 4곳, 노인 병원 1곳, 보건소 1곳, 복지관 3곳, 보육시설 2곳)을 대상으로 수행하였다. 1. 포름알데히드의능동 포집법(공정시험법)에 의한 시료(n=87)의 평균농도는 $11.44{\pm}11.07ppb$이고, 확산형 시료 채취기 의한 시료(n=40)의 평균농도는 $11.91{\pm}7.37ppb$으로 비슷한 값이 나왔고, 통계적으로 유의하지 않았다(p=0.806). 2. 포름알데히드 능동 포집법에 의한 농도와 확산형 시료 채취기에 의한 농도와의 상관계수 r=0.404(p=0.037)로 나타나 이 두 가지의 방법은 특정시간 포름알데히드 측정에 사용하여도 어느 정도 비교하기에는 적합할 것으로 생각된다. 3. 이산화질소의 노출정도는 직독식 기기(공정시험방법)와 확산형 시료 채취기로 각각 1시간 (오전, 오후 각각 2회), 8시간 측정하였다. 공정시험방법(n=61)에 의한 1시간-시료 평균농도는$44.48{\pm}37.96ppb$이고, 확산형 시료 채취기(n=61)에 의한 1시간-시료 평균농도는 $3.58{\pm}2.07ppb$으로 통계적으로 유의하였다(p=0.000). 직독식 기기(n=61)에 의한 8시간-시료 평균농도는 $34.85{\pm}22.83ppb$이고, 확산형 시료 채취기(n=61)에 의한 8시간-시료 평균농도 $8.32{\pm}4.44ppb$으로 통계적으로도 유의하였다(p=0.000). 4. 이산화질소를 직독식 기기(공정시험방법)와 확산형 시료 채취기로 측정한 1시간-시료 농도의 상관계수 r=0.253(p=0.268)이고 8시간-시료 일 때 상관계수 r=0.367(p=0.102)로 나타나 확산형 시료 채취기를 직독식 기기(공정시험방법) 대체 사용방법으로 이용하기에는 적합하지 않다고 생각된다.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.44-45
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• 2003

전자기 유도 투과란 매질 속을 진행하는 빛의 투과가 다른 강한 빛의 작용으로 증가하게 되는 결맞음 현상을 말한다. 이러한 전자기 유도 투과는 또한 굴절율의 변화를 동반하게 되며, 그 결과 매질을 진행해 나가는 레이저빔은 유도 집속 및 확산, 또는 자체집속 및 확산의 제거 등을 겪게 된다. 이러한 원리를 이용하여 M. Jain 등은 납 증기에서 원공명 조건의 결맞음 밀도 포획을 이용한 자체집속의 제거에 성공한바 있다. (중략)

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.1
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• pp.75-78
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• 2013

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.9
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• pp.1884-1891
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• 2012

In this paper, we design the sliding correlator SS transceiver which supports short message service. We also analyze the PN code acquisition circuit that is essential for spread spectrum receiver. Using Maxplus II tool provided by altera Co., Ltd, we have designed PN code generator, and sliding correlator for PN code acquisition. Then, they have been made into FPGA by way of EPM7064SLC44-10 - a chip of Altera Co., Ltd. Additionally, we have designed delay clock circuit which is faster than the clock of Tx PN clock, designed switching circuit to control the clock rate and data demodulation circuit. The performance of the transceiver is evaluated from the experimental results. Especially, the performance of PN code acquisition accomplished by sliding correlator which is very important to evaluate spread spectrum receiver is evaluated with the comparison of the lock states.