• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.5
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• pp.877-886
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• 2019

The energy band gaps and optical constants of zincblende $In_yGa_{1-y}As_{1-x}N_x$ on the variation of temperature and composition are determined by using band anticrossing method. The energy band gaps are decreasing continuously in $In_yGa_{1-y}As_{1-x}N_x$ ($0{\leq}x{\leq}0.05$, $0{\leq}y{\leq}1.0$, 300K) and the bowing parameter is calculated as 0.522eV. The calculation results of energy band gaps are consistent with those of other studies. A refractive index n and a high-frequency dielectric constant ${\varepsilon}$ are calculated by a proposed modeling equation using the results of energy band gaps.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.12
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• pp.1165-1174
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• 2016

The energy band gaps and the bowing parameters of zincblende InAs1-xN are determined by using an empirical pseudopotential method(EPM) within the improved virtual crystal approximation(VCA), which includes the disorder effect. The direct-band-gap bowing parameter calculated by using the EPM is 4.1eV for InAs1-xNx ($0{\leq}x{\leq}0.05$). The dependences of the band gaps of N-dilute InAs1-xNx on the temperature and composition are calculated by modifying the band anti-crossing(BAC) model. The calculation results are consistent with experimental values, and the coupling parameter CMN of InAs1-xNx is found to be equal to 1.8 by fitting the EPM data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1B
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• pp.89-98
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• 2000

This paper presents an active noise cancelling model using wavelet transform and subband filter banks based on adaptive filter. The analysis filter banks decompose input and error signals into QMF filter banks of lowpass and highpass bands. Each filter bank uses wavelet filter with dyadic tree structure. The decomposed input and error signals are iterated by adaptive filter coefficients of each subband using filtered-X LMS algorithm. The synthesis filter banks make output signal of wideband with perfect reconstruction to prepare adaptive filter output signals of each subband. The analysis and synthesis niter hants use conjugate quadrature filters for Pefect reconstruction. Also, The delayed LMS algorithm model for on-line identification of error path transfer characteristics is used gain and acoustic time delay factors. The proposed adaptive active noise cancelling modelis suggested by system retaining the computational and convergence speed advantage using wavelet subband filter banks.

• Journal of the Korean earth science society
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• v.40 no.5
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• pp.447-463
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• 2019

Sea surface wind is a fundamental element for understanding the oceanic phenomena and for analyzing changes of the Earth environment caused by global warming. Global research institutes have developed and operated scatterometers to accurately and continuously observe the sea surface wind, with the accuracy of approximately ${\pm}20^{\circ}$ for wind direction and ${\pm}2m\;s^{-1}$ for wind speed. Given that the spatial resolution of the scatterometer is 12.5-25.0 km, the applicability of the data to the coastal area is limited due to complicated coastal lines and many islands around the Korean Peninsula. In contrast, Synthetic Aperture Radar (SAR), one of microwave sensors, is an all-weather instrument, which enables us to retrieve sea surface wind with high resolution (<1 km) and compensate the sparse resolution of the scatterometer. In this study, we investigated the Geophysical Model Functions (GMF), which are the algorithms for retrieval of sea surface wind speed from the SAR data depending on each band such as C-, L-, or X-band radar. We reviewed in the simulation of the backscattering coefficients for relative wind direction, incidence angle, and wind speed by applying LMOD, CMOD, and XMOD model functions, and analyzed the characteristics of each GMF. We investigated previous studies about the validation of wind speed from the SAR data using these GMFs. The accuracy of sea surface wind from SAR data changed with respect to observation mode, GMF type, reference data for validation, preprocessing method, and the method for calculation of relative wind direction. It is expected that this study contributes to the potential users of SAR images who retrieve wind speeds from SAR data at the coastal region around the Korean Peninsula.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.2
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• pp.89-95
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• 2003

This paper proposes downlink blocking model and approximation equation using lower bound approximation in order to determine the proper guard band between cdma2000 1X and WCDMA in handover areas. The frequency sharing conditions obtained by the model and approximation equation on blocking probability proposed in the paper, are co-site of base station and guard band higher than 1 MHz. Also, the proposed equation is in the form of Q-function. It is an analytical solution overcoming the drawback of recalculation, belonged to Monte-Carlo technique.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.225-225
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• 2010

적외선 영역에서의 밴드갭 에너지를 가지고 있는 III-V 족 화합물 반도체 물질인 $InAs_xSb_{1-x}$는 좋은 성장 안정성과 높은 전자, 홀 이동도를 가지며, 제작 비용이 적게 드는 등 적외선 광소자 제작에 많은 이점을 가지고 있기 때문에 그에 관한 연구가 최근 활발히 진행 되고 있다. 하지만 이러한 $InAs_xSb_{1-x}$를 소자 제작에 이용하기 위해서는 임의의 As 함량에 따른 InAsSb의 물질의 광학적 특성 정보가 필요하다. 본 연구에서는 1.5~6.0 eV 에너지 구간에서 $InAs_xSb_{1-x}$ ($0{\leq}x{\leq}1$) 화합물의 임의의 As 함량에 따른 유전함수를 분석하고 그 분석 변수들을 보고하고자 한다. 기성박막층착장치 (molecular beam epitaxy)를 이용하여 GaAs 기판 위에 성장 시킨 $InAs_xSb_{1-x}$ (x = 0.000, 0.127, 0.337, 0.491, 0.726, 1.000) 박막의 순수한 유전함수 $\varepsilon$을 화학적 에칭을 통해 산화막 층을 제거하여 타원편광분석법을 이용하여 얻었다. 측정된 유전율 함수는 Gaussian-broadened polynomial 들의 합으로서 반도체 물질의 유전함수를 정확히 기술하는 변수화 모델을 이용하여 재현하였다. 변수화 모델을 통해 얻어진 각각의 변수들을 As 조성비 x 에 대한 다항식으로 피팅하여 임의의 As 조성비에 대한 변수 값을 얻었다. 그 결과 임의의 조성비에 따른 $InAs_xSb_{1-x}$ ($0{\leq}x{\leq}1$) 의 유전율 함수를 얻어낼 수 있었다. 우리는 이러한 결과가 물질의 실시간 성장 모니터링이나 다층구조 분석, 광소자의 제작 등에 유용한 정보를 제공할 것으로 확신한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.8
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• pp.801-808
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• 2004

In this paper, we proposed the grating parallel plate waveguide structure for converting a linearly polarized wave to a circularly polarized wave. For the design of the polarizer, the moment method and Floquet's theorem are applied under two assumptions that the incident wave is a plane wave and the structure is infinitely periodic. In order for the more precise design, we performed the near-field analysis for the finite polarizer structure using MATLAB. By comparing with the measured results obtained by the near-field arrangement, we verified the correctness of our near-field analysis. By taking the ideal assumptions considered in the initial design procedure into account, newly designed modified dimensions for the polarizer was suggested which give improved performance.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.4
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• pp.535-540
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• 2013

We design a slotted waveguide antenna for X-band which a 1.4m length with slot depth variation. A 54 slot array is modeled and simulated by CST, and the side lobe level is suppressed effectively in a certain range of frequency. The experimental results of the antenna show that its gain, maximum sidelobe level and half power beam-width are 21.8dB, -31dB and 2.0deg, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.11
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• pp.1019-1025
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• 2004

The X-band 10${\times}$10 waveguide slot array antenna for SAR is designed, fabricated and measured. The array antenna is designed using the equivalent circuit model based on the field distribution of the dominant mode, TE$\sub$10/, and EM simulation. The method to decide optimum angle of the centered inclined slot(coupling slot) and the optimum of offset of the longitudinal slot(radiating slot) is provided. The designed antenna structure is EM simulated and fabricated. The measured return loss bandwidth is 180 MHz at 9.15 GHz , the side lobe level is below -25 dB, HPBW is about 9$^{\circ}$, and the gain is 25.5 dB. These results are similar to the simulation data.

• Journal of the Korean Magnetics Society
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• v.8 no.3
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• pp.111-117
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• 1998

Recent discovery of colossal magnetoresistance (CMR) phenomena in perovskite manganese oxides has evoked great interest for its physical peculiarity and the possible industrial application. Besides manganese oxides, CMR phenomena is also observed in $Tl_2Mn_2O_7$ with pyrochlore structure and in Cr-based chalcogenide with spinel structure. In this paper, we have studied electronic structures of Cr-based chalcogenide spindles $Fe_{1-x}Cu_xCr_2S_4$ at x=0.0, 0.5, 1.0 using the linearized muffin-tin orbital (LMTO) band method within the local density approximation (LDA). The characteristic resistivity for x=0.0, 0.5 could be explained qualitatively in terms of the half-metalic electronic structure and the Jahn-Teller effect. Especially, the half-metallic nature appearing in the metallic temperature regime is well descibed by the proposed conduction model for x=0.0, 0.5, 1.0. We have suggested, based on the conduction model, that the CMR phenomena observed in these compounds are closely correlated with the obtained half-metallic electronic structure.