• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.2
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• pp.247-254
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• 2021

Problems such as a limited frequency resource and interference between adjacent bands have been continuously raised because of rapidly developing wireless technology and communication service. In order to solve that problem, government has been developed and operating the Spectrum Management Intelligent System(SMIS). This paper compares the results simulated by SMIS with the ATDI and the Matlab coded provided by ITU-R for verification of SMIS operating for the public interests. The Recommendation ITU-R P.526, P.1546, and P.1812 among the propagation model loaded in SMIS were chosen because of the relation to the broadcasting service. The comparison and analysis result shows that the outputs derived by SMIS has the small error of less than 1 dB. This research could be utilized for the policy establishment and R&D for the frequency allocation and the interference between adjacent bands.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.1
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• pp.12-22
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• 2019

This paper presents a method to perform a more efficient electromagnetic wave analysis inside a large building by external electromagnetic waves. Topological analysis and the PWB method are introduced for electromagnetic wave analysis. In addition, a Performance-Enhanced PWB method, which complements the performance of the PWB method is proposed. A large virtual structure was selected and an analysis environment was set up to perform the electromagnetic wave analysis inside a large building from external electromagnetic waves. A commercially available software, Wireless Insite, was used to verify the accuracy of the the Performance- Enhanced PWB method. As a result of comparing the two results in terms of accuracy, time, and memory, We conclude that the Performance-Enhanced PWB method proposed in this paper is a more efficient method in a large bulding.

• Journal of IKEEE
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• v.23 no.3
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• pp.1108-1111
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• 2019

This paper presents the comprehensive transformer design methodology with the winding method of automatic type suitable for LLC resonant converter. The problem with conventional LLC resonant transformer is that it is difficult to implement the winding method of automatic type because all windings are wound in one bobbin. Therefore, the LLC resonant transformer, which is capable of the winding method of automatic type to multiple section bobbin without insulation tape and barrier tape, is proposed in this paper and the design procedure of the proposed LLC resonant transformer is also shown. Modeling and analysis of the proposed LLC resonant transformer using Maxwell 3D simulation tool are described in detail and a protype 150W LLC resonant converter using the proposed LLC resonant transformer manufactured by 3D modelling is also verified through the experimental test.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.1
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• pp.1-8
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• 2021

In this paper, the cabinet shielding effectiveness (SE) including digital modules for nuclear power plants is analyzed depending on the internal structure and electromagnetic (EM) wave incidence angle. To analyze the SE, the cabinet and modules are modeled using the FEKO EM simulation tool. The SE is then obtained by comparing the electric field with and without the cabinet. In addition, the cabinet SE is observed by changing various conditions such as the spacing of each digital module, incidence angle, and the polarization of the EM wave at the 2.4 G[Hz frequency. To verify the results, the dipole antenna for SE measurements is fabricated, and the SE is measured in a semi-anechoic chamber. The result demonstrates that the SE by the cabinet structure can be expected to be higher when the polarization of the incident EM wave is horizontal to the ground and the distance between the digital modules is wide.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.6
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• pp.975-980
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• 2020

To protect wireless sensor networks (WSNs), various key distribution and management schemes have been proposed. However, most of them conducted simulations and experiments for performance evaluation by considering only the two-dimensional (2D) environments. In this paper, we investigate the effect of real-world three-dimensional (3D) topographic features on the key pre-distribution schemes for WSNs. For this purpose, we analyze and compare the performance of three pairwise key pre-distribution schemes in 2D and 3D environments: full pairwise (FP), random pairwise (RP), and full and random pairwise (FRP) schemes. For the experiments, we employ a network simulator NS-3 and 3D graphic tools such as Blender and Unity. As a result, we confirm that there was a difference in the performance of each scheme according to the actual 3D terrain and that the location-based FRP that considers deployment errors, has the highest efficiency in many aspects.

• Journal of The Korean Association of Information Education
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• v.24 no.6
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• pp.597-606
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• 2020

Recently, as students' programming classes are being conducted online, interest in factors that can lead to the success of online programming classes is also increasing. Therefore, in this study, online programming classes were conducted for specialized high school students using a web-based simulation programming tool through TinkerCad. In these online programming classes, students' self-regulation ability and learning flow were set as variables that influence both learning engagement and teaching presence, and the predictive power of each was analyzed. As a result, it was found that both self-regulation ability and learning flow were predictive variables for learning engagement and teaching presence, and that learning flow played a mediating role between self-regulation ability, learning engagement, and teaching presence. This study is meaningful in that it suggested that self-regulation ability and learning flow should be considered more meaningfully in online programming classes, and a practical strategy for this is presented.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.7
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• pp.1032-1039
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• 2022

In this paper, we designed and implemented a cavity bandpass filter combined with a cross-coupling equalizer structure to enhance Group delay for 5G mobile network repeater, which can replace the SAW (Surface Acoustic Wave) type bandwidth filter used in the existing mobile communication system. Using the 3D EM simulation tool (HFSS), the resonance frequency, the coupling coefficient between resonators, and external quality coefficient between resonators were calculated. Based on this, a 12th bandpass filter was constructed to have attenuation characteristics of more than 20dB at the edge end of both sides of the band with a metal cavity structure with a frequency band of 3500MHz to 3600MHz and bandwidth of 97.85MHz. The designed bandpass filter satisfies the group delay time requirement for the 5G mobile communication standard and the in-band and out-band frequency responses.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.11
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• pp.523-530
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• 2018

It has been studied over the long time for the high efficiency and high power density of the power converter. It is possible to obtain higher power conversion efficiency and small volume by increasing switching frequency, however, the switching loss is also increased. The soft switching technique can overcome of the above deficiency. The design and analysis method for ZVS(Zero Voltage Switching) Phase Shifte Full bridge converter is presented in this paper. The power transfer depends on the phase difference between two legs of the power stage and the maximum power conversion efficiency is achieved by the optimum leakage inductance value. The waveform of the current and voltage of the operational mode is analysed and the corresponding switch status is plotted as on/off status. A ZVS full bridge converter for a communication rectifier with 2kW output power is implemented and its performance are verified through PSIM software simulation and experimental results.

• Journal of Convergence for Information Technology
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• v.10 no.9
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• pp.1-7
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• 2020

In order to implement a smart factory for manufacturing innovation, more digital twins will be developed and applied gradually. In particular, simulation and optimization of digital twins makes it possible to support critical decision-making like a predictive maintenance of the equipment for manufacturing. In terms of a user perspective, this study suggests the conceptual framework of Digital Twin Management System (DTMS) for supporting the analytical and managerial activities for Digital Twins. We integrate the methods and structure of the area like Manufacturing Engineering, Decision Support Systems, and Optimization for developing the DTMS. The framework suggested in this study shows a typical DSS which consists of dialog management system, model management system and data management system. It also includes Analytical Digital Twins and simulations & optimization module. The framework is being applied in one of the most competitive and complex industrial sector. Also this study is meaningful to suggest a new direction of research.

• Journal of Satellite, Information and Communications
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• v.12 no.3
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• pp.80-85
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• 2017

In this paper, a mircrowave breakdown of X-band circular waveguide cavity filter, which occurred during ground test, was introduced, and electro-magnetic field simulation results to identify a root cause, and the analysis of possibility of its occurrence on orbit operation were presented. Filter modeling for simulation was conducted with a commercial tool (FEST3D), and electric fields inside the filter were monitored at the input of 1 W continuous wave. In our observation, strong electric field intensities were monitored on the tuning screws especially at the input of band-edge frequencies. The threshold power levels for the breakdown were also estimated and compared with the input power levels actually injected to the filter. From this estimation, we could figure out that the power exceeding the breakdown threshold was injected to the filter so that strong electric fields were generated and temperature increased high, and this became a root cause of the electrical short. Our further analysis showed that this kind of microwave breakdown is not likely to occur on orbit operation, and multipactor is expected not to occur at the input of band-edge frequencies. As a measure to prevent the microwave breakdown, we suggested to avoid the injection of band-edge frequencies and inject lower power levels to the filter.