• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.1
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• pp.9-14
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• 2005

Mode missing of Fabry-Perot laser diodes has been modeled using the time domain laser model(TDLM). Fabry-Perot laser diodes that have structure of ripple in the waveguide of active layer or defects inside the active layer were simulated. For accurate simulation, the nonlinear effects were included such as spatial hole burning(SHB) and gain saturation. From the simulation results, it was founded that the defect inside the active layer in laser diodes has a strong influence on mode missing rather than the waveguide ripple. The simulation results are confirmed with the fabricated Fabry-Perot laser diodes by measuring the longitudinal mode spectra as a function of temperature from $25[^{\circ}C]\;to\;85[^{\circ}C]$.

• The Journal of the Acoustical Society of Korea
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• v.34 no.5
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• pp.360-370
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• 2015

In case that an infinite length waveguide structure is connected with a finite length structure, it is required to combine a wave approach for the waveguide structure and a modal approach for the finite length structure to investigate the dynamic response of the connected target structure. In this study, the wavenumber finite element (WFE) analysis is adopted for the infinite length waveguide substructure and a finite element (FE) method is applied for the finite length substructure and then their results are coupled in terms of the impedance or mobility at the connected points between the substructures. As a structural model, an infinite length cylindrical shell with a rectangular plate inside is regarded. These two substructures are connected at the four corner points of the plate, rigidly or resiliently. From this investigation, it was confirmed that the wave approach (WFE method) and modal approach (FE method) can be combined by the impedance coupling.

• Journal of electromagnetic engineering and science
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• v.2 no.2
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• pp.100-104
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• 2002

A proper equivalent circuit model for coupling iris has been derived in order to compensate the length of cavity in a $TE_{011}$TEX> mode cylindrical cavity filter. A method to resolve the difference in bandwidth and feature or ripple systematically has been proposed. This method can be applied to other types of waveguide cavity filter.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1986.10a
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• pp.20-22
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• 1986

This paper represents a graphical design technique of the symmetrical dielectric waveguids couplers. Once the phase constants are given by a approzimate model analysis, coupling lengths are easily calculated for each coupler. These method give some new insight of the codirectional couplers.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.147-151
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• 2000

This paper presents an analysis of a slot on the broad wall of a rectangular waveguide using the 3D FDTD method. In order to reduce the reflection loss, Mur's 2nd absorbing boundary condition is used. To realize the optimum design by FDTD, the effects of time step, excitation aperture size, analysis region and excitation position in model are derived. The analysis results are compared with the experimental results and they show a good agreement with each other.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.5
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• pp.985-988
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• 2017

Magnetic induction (MI) based communication is one of the near-field communication techniques, which makes use of induced magnetic fields. In order to develop the MI based underwater communication networks, we evaluate and compare the loss performance between direct-MI and MI-waveguide in underwater environment.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.6
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• pp.263-267
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• 2004

A new type of interaction circuitry for a broadband gyro-TWT is presented in this paper. A method for the analysis of dispersion characteristics of a periodic structure, which is composed of conducting posts in a rectangular waveguide, is presented. This method utilizes a mode matching technique and equivalent circuit model. The calculated and measured results demonstrate that this periodic structure could be utilized for the interaction circuit of a wide band Gyro-TWT.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.3
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• pp.241-262
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• 2012

Some applications require structural health monitoring in inaccessible components. This paper presents a technique useful for Structural Health Monitoring of double wall structures, such as double wall steam pipes and double wall pressure vessels separated from an ultrasonic transducer by three layers. Detection has been demonstrated at distances in excess of one meter for a fixed transducer. The case presented here is for one of the layers, the middle layer, being a fluid. For certain transducer configurations the wave propagating in the fluid is a wave with low velocity and attenuation. The paper presents a model based on wave theory and finite element simulation; the experimental set-up and observations, and comparison between theory and experiment. The results provide a description of the technique, understanding of the phenomenon and its possible applications in Structural Health Monitoring.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.04a
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• pp.273-276
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• 2002

본 논문에서는 Physical Modeling을 이용해 단소의 음을 합성해 내는 방법에 대해 연구 하였다. 현재 관 악기의 음 합성 방법은, Julius O. Smith가 제안한 digital waveguide모델을 근간으로 하여 여러 악기들의 소리를 합성하는 방법에 대해 연구 되고 있다. 본 논문에서는 digital waveguide모델을 사용하여 단소 관속의 움직임, two-port scattering model을 이용한 관속과 음공 사이의 공기의 움직임에 대해 기술하였고, reflection filter를 사용하여 단소 끝부분에서의 신호의 변화에 대해 연구 하였으며, 끝으로 관 내벽과 공기의 마찰에 의한 신호 손실에 대한 연구를 기술 하였다. 위에서 언급한 내용들의 연구결과를 토대로 음을 합성한 결과 실제 단소의 소리와 유사한 소리를 얻어 낼 수 있었다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.1980-1985
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• 2010

This paper is about design of optimal structure of slot antenna array antenna with inner waveguide in accordance with the slot model, and fabrication of its prototype sample operating at the frequency of 24 GHz. Results of this work can be employed as a useful tool to develop and diversify slot antenna having superior performance and omni-directivity to that of current antenna. The implemented antenna demonstrates ultra-wideband performance for frequency ranges 24 GHz with the relatively high and flat antenna gain of 18.64dBi and low sidelobe levels. In addition, a $2{\times}8$ antenna array for phased-array systems and mm-wave sensor applications is also presented.