• KIEE International Transactions on Electrophysics and Applications
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• 제2C권5호
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• pp.268-272
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• 2002

In this paper, we proposed a procedure to analyze a shielded-microstrip step discontinuity using the mode matching method (MMM) combined with the vector finite element method (VFEM), which is used to find the equivalent waveguide-model for a microstrip. In order to calculate the effective-widths and -dielectric permittivity of the equivalent waveguide-model corresponding shielded-microstrip, the propagation constant and characteristic impedance are calculated from the VFEM. MMM is then applied to find the scattering parameter in the planar waveguide. This technique makes it possible to take advantage of the high accuracy of the VFEM as well as the high efficiency of the MMM.

• 전자공학회논문지SC
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• 제49권3호
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• pp.75-81
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• 2012

최근에 소개된 능동 FSS(active frequency selective surface) 또는 ESS(electromagnetic smart screen)는 2차원 금속섬유 복합재료에서 금속섬유의 부하저항을 변화시킴으로써 복합재료의 분산특성을 변경시키는 기술이다. 본 논문에서는 부하저항의 변화에 따른 ESS의 분산특성을 효율적으로 계산하기 위해 GEC(generalized equivalent conductor) 기법을 기반으로 수정하여 적용한다. 부하저항에 따른 ESS의 투과계수와 유효유전율을 1~40 GHz의 범위에서 시뮬레이션 한다. 또한, 부하저항을 변경함으로써 공진주파수와 대역폭을 변경할 수 있음을 보인다.

• ETRI Journal
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• 제38권1호
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• pp.141-148
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• 2016

This paper proposes a method to estimate directly the incoherent scattered intensity and radar cross section (RCS) from the effective permittivity of a random media. The proposed method is derived from the original concept of incoherent scattering. The incoherent scattered field is expressed as a simple formula. Therefore, to reduce computation time, the proposed method can estimate the incoherent scattered intensity and RCS of a random media. To verify the potential of the proposed method for the desired applications, we conducted a Monte-Carlo analysis using the method of moments; we characterized the accuracy of the proposed method using the normalized mean square error (NMSE). In addition, several medium parameters, such as the density of scatterers and analysis volume, were studied to understand their effect on the scattering characteristics of a random media. The results of the Monte-Carlo analysis show good agreement with those of the proposed method, and the NMSE values of the proposed method and Monte-Carlo analysis are relatively small at less than 0.05.

• Journal of Magnetics
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• 제21권2호
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• pp.187-191
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• 2016

Retrieving the equivalent electromagnetic parameters (permittivity and permeability) plays an important role in the research and application of metamaterials. Frequency dispersion of magnetic permeability has been theoretically predicted in a metamaterial composed of cut wire pairs (CWP) separated by dielectric substrate on the basis of circuit theory. Magnetic resonance resulting from antiparallel currents between the CWP is observed at the frequency of minimum reflection loss (corresponding to absorption peak) and effective resonator size can be determined. Having calculated the circuit parameters (inductance L, capacitance C) and resonance frequency from CWP dimension, the frequency dispersion of permeability of Lorentz like magnetic response can be predicted. The simulated resonance frequency and permeability spectra can be explained well on the basis of the circuit theory of an RLC resonator.

• 한국전자파학회논문지
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• 제8권5호
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• pp.534-544
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• 1997

Levenberg-Marquardt (LMA)와 유전 알고리즘(GA)을 결합한 새로운 잡종알고리틈을 반복적으로 사용하여, 비용함수의 실 극소값(global minimum)을 주는 2차원 강산란체의 유전율 분포를 재구성한다. 비용함수에 사용되는 산란파는 원통형 각모드로 전개되며, 이 중 유효 전파모드만이 이용된다. 유효 전파모드만을 사용하여 비용함수를 정의함으로써 주어진 산란체를 재구성하는데 필요한 입사파 개수의 최소값이 공식화된다. 수치해석 결과로부터,LMA는 수렴 속도가 빠르나 강산란체를 재구성할 수 없고, GA는 강산란체의 재구성은 가능하나 수렴 속도가 느린 반면, 결합 알고리즘을 이용하는 역산란 방법은 LMA와 GA의 장점만을 취합한 방법임이 입증된다.

• 한국지반공학회논문집
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• 제25권6호
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• pp.17-29
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• 2009

에너지 수요의 증가 및 에너지 탐사와 연관되어 해저 지반의 조사가 증가하고 있다. 해수면 2100m 해저 110m 아래에서 얻어진 압력 코어 시료의 메탄 하이드레이트 생산 시험 후 얻어진 사료를 이용하여 울릉 분지 심해토의 지반공학적 특성을 조사하였다. 기본 토성, 광물학적 특성, 화학 조성, 그리고 미세구조 관찰을 위하여 토성 실험, XRD, 그리고 SEM을 실시하였다. 또한, 멀티 센서 압밀셀을 이용하여 두 시료의 압축성, 전단파 및 전자기파 파악하였다. 강도특성은 직접전단실험 이용하여 산정되었다. 주요 광물로는 카오리나이트, 일라이트, 크로라이트(chlorite), 그리고 캘싸이트(calcite)가 관찰되었다. SEM 결과 잘 발달된 내 외부 간극 구조가 관찰되었다. 수직유효응력의 증가에 따라 전단파 속도, 전기비저항, 실수 유전율, 그리고 전기전도도는 이중선형 거동을 보였다. 직접전단실험으로 얻은 마찰각은 약 $21^{\circ}$로 선행연구와 비슷한 결과를 보였다. 본 연구는 가스 하이드레이트와 같은 에너지 자원의 개발 및 새로운 지반공학적 영역의 확보를 위하여 심해 퇴적토의 거동 이해의 중요성을 보여준다.

• 조명전기설비학회논문지
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• 제26권2호
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• pp.99-105
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• 2012

This paper deals with the experimental results of the frequency-dependent resultant ground impedance of vertical ground electrodes installed with a regular n-polygon. In order to propose an effective method of installing the vertically-driven multiple ground electrodes used to obtain the low ground impedance, the resultant ground impedance of ground electrodes installed with a regular n-polygon were measured as functions of the number of ground electrodes and the frequency of test currents and the results were discussed based on the potential interferences among ground electrodes. As a consequence, the effect of potential interference on the resultant ground impedance of vertical ground electrodes is frequency-dependent and it is significant in the low frequency of a few hundreds [Hz]. The resultant ground impedance of multiple vertical ground electrodes is not decreased in linearly proportion to the number of ground electrodes due to the overlapped potential interferences. Also the distributed-parameter circuit model considering the potential interference, the frequency-dependent relative permittivity and resistivity of soil was proposed. The simulated results of the frequency-dependent resultant ground impedance of multiple vertical ground electrodes are in good agreement with the measured data.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.141-145
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• 2005

Since the electromagnetic properties of fiber reinforced polymeric laminate composite can be tailored effectively by adjusting its composition and regulating the stacking sequence, it is plausible material for fabricating the radar absorbing structures (RAS) of desired performance. In order to design the effective electromagnetic wave (EM) absorber with the fiber reinforced polymeric laminate composite, its electromagnetic characteristics should be available and could be regulated easily in the target frequency bands. In this study, dielectric characteristics of the E-glass/epoxy laminate composites were measured by the free space method in the X-band frequency range ($8.2\;{\sim}\;12.4\;GHz$). In order to describe the dielectric behavior of laminate composites of arbitrary stacking sequences, the equivalent circuit model and the laminating equations for estimating dielectric properties were proposed, and experimentally verified. From the comparison of the predicted and measured data, the proposed method predicted well the experimentally measured data.

• 한국재료학회지
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• 제12권2호
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• pp.160-165
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• 2002

High-frequency dielectric and microwave absorbing properties have been investigated in ferroelectric materials (BaTiO$_3$(BT), (1-x)Pb$Mg_{\frac{1}{3}}Nb_{\frac{2}{3}}$)O$_3$-xPbTiO$_3$(PMN-PT), (1-x)Pb$Mg_{\frac{1}{3}}Nb_{\frac{2}{3}}$O$_3$-xPb(Zn_{\frac{1}{3}}Nb_{\frac{2}{3}}$)O$_3$(PMN-PZN) for the aim of thin microwave absorbers in the frequency range of mobile telecommunication. The specimenns are prepared by conventional ceramic processing and complex permittivity has been measured by transmission/reflection method. The ferroelectric materials show high dielectric constant and dielectric loss in the microwave range and their domiant loss mechanism is considered to be domain wall relaxation. The microwave absorbance of BT 0.9PMN-0.1PT, and 0.8PMN-0.2PZN specimen (determined at 2) are found to be 99.5% (at a thickness of 4.5 mm), 50% (2.5 mm), and 30% (2.5 mm), respectively. It is suggested that PMN-PT or PMN-PZN ferroelectrics are good candidate materials for the spacer of λ/4 absorber. The use of ferroelectric materials is effective in reducing the thickness of absorber with their advantage of high dielectric constant.

• 한국컴퓨터정보학회논문지
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• 제3권3호
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• pp.107-112
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• 1998

본 논문에서는 마이크로스트립 선로로 제작이 쉽고, 스터브를 사용한 필터보다 적은 공간을 차지하는 Hi-Z, Low-Z 필터를 사용하여 마이크로스트립 필터를 설계.제작하였다. 이 필터는 선로의 전기적 길이가 매우 짧은 경우. 즉 Bl＜$\pi$/4의 조건에서, 저역통과기본형의 직렬 인덕터일 때 고 임피던스 선로부로 병렬 커패시터를 저 임피던스 선로부로 대치할 수 있다. 이렇게 대치된 각 단을 마이크로스트립 선로로 설계하기 위해 주어진 마이크로스트립의 실효 유전율을 구해서 각 단의 폭과 길이를 계산하고 필터 설계에 사용하였다. 또한, 설계된 필터를 Touchstone의 이론치와 제작된 필터의 실험치를 비교하여 응답특성을 분석하였다.