• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.72-73
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• 2016

In this paper, we studied a method for miniaturizing a broadband stacked patch antenna structure which is widely used for bandwidth improvement. Main patch is a rectangular microstrip patch antenna fed by a 50-ohm microstrip line, and a parasitic patch is laid above the main patch. The size of the main patch is designed to be resonated near the center frequency of the desired frequency band. Then parasitic patch longer than main patch is placed above the main patch. The distance between two patches might be adjusted so as to achieve impedance matching using a shunt open stub. The shunt matching stub is inserted underneath the parasitic patch and so it does not require additional space, which enables the proposed antenna structure to be advantageous in miniaturizing antenna. The effects of the various parameters on the antenna performance are examined, and we introduced the design procedure for the proposed antenna to operate in the frequency range of 2.3-2.7 GHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.12
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• pp.1659-1665
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• 2019

In this paper, a novel design of a compact printed monopole antenna for wireless local area network (WLAN) applications is investigated. The radiator with a patch of different line width and step-shaped ground planes is used to reduce the antenna size. The size of the antenna is 16 × 17 × 1 ㎣ and is fabricated with a photolithography technique. The simulated and measured results agree well. The resonant frequency of the investigated antenna is about 5.2 GHz and can cover an impedance bandwidth of 1 GHz for the measurement result. In addition, we presented the measured radiation pattern, presented the gain and efficiency measured in the required WLAN 5 GHz frequency band (5.15-5.825 GHz), and confirmed that it can be used as a 5 GHz band WLAN antenna. The investigated antenna has a small size, light weight, low cost, omni-directional radiation pattern, high gain, and high efficiency.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.6_2
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• pp.1071-1081
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• 2022

As the demand for high-rise buildings increases, the demand for high-speed elevators is also increasing. In order to make a high-speed elevator, a method is needed to reduce the weight of the elevator's components, which is a constraint on the increase in speed. As a measure to reduce the weight, it is possible to remove the traveling cable for power and signal supply. Since the weight of the traveling cable varies depending on the position of the carriage, it is difficult to compensate the weight using the counter weight. The power supply is a structure in which a brush-rail type power input terminal is installed in the elevator hoistway to receive power in a contact-type manner while the carriage is moving. If a small-capacity ESS is installed in a passenger car, power can be supplied uninterruptedly inside the passenger car. A small-capacity ESS charging system to be applied to such an elevator system is required to perform several functions. First, the passenger Car must be able to charge as much as possible even during high-speed operation. A control algorithm with high responsiveness is required because charging starts and ends repeatedly by the partially installed input power stage. In addition, if the input-side line impedance is large due to the structure of the system and the response characteristic is increased, the stability of the system may be lowered. Accordingly, in this paper, we propose a control algorithm that has a stable steady-state output while having a fast response in a transient state. To verify the proposed control algorithm, simulation was conducted using PSIM, and the performance of the controller was verified by manufacturing a prototype buck conveter charger.

• International Journal of Computer Science & Network Security
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• v.22 no.12
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• pp.245-251
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• 2022

In this paper, a high gain, broadband planar vivaldi antenna (PVA) by utilizing a broadband stripline feed is developed for wireless communication for IoT systems. The suggested antenna is designed by attaching a tapered-slot construction to a typical vivaldi antenna, which improves the antenna's radiation properties. The PVA is constructed on a low-cost FR4 substrate. The dimensions of the patch are 1.886λ₀×1.42λ₀×0.026λ₀, dielectric constant Ɛ_r=4.4, and loss tangent δ=0.02. The width of the feed line is reduced to improve the impedance bandwidth of the antenna. The computed reflection coefficient findings show that the suggested antenna has a 46.2% wider relative bandwidth calculated at a 10 dB return loss. At the resonance frequencies of 6.5 GHz, the studied results show an optimal gain of 5.82 dBi and 85% optimal radiation efficiency at the operable band. The optometric analysis of the proposed structure shows that the proposed antenna can achieve wide enough bandwidth at the desired frequency and hence make the designed antenna appropriate to work in satellite communication and medical internet of things (M-IoT) healthcare applications.

• Journal of the Korea Society of Computer and Information
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• v.28 no.12
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• pp.221-229
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• 2023

Recently, Grid-forming(GFM) converter, which offers features such as virtual inertia, damping, black start capability, and islanded mode operation in power systems, has gained significant attention. However, in low-voltage microgrids(MG), it faces challenges due to the coupling phenomenon between active and reactive power caused by the low line impedance X/R ratio and a non-negligible power angle. This power coupling issue leads to stability and performance degradation, inaccurate power sharing, and control parameter design problems for GFM converters. Therefore, this paper serves as a review study on not only control methods associated with GFM converters but also power decoupling techniques. The aim is to introduce promising control methods and enhance accessibility to future research activities by providing a critical review of power decoupling methods. Consequently, by facilitating easy access for future researchers to the study of power decoupling methods, this work is expected to contribute to the expansion of distributed power generation.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.2
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• pp.361-370
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• 2024

In this paper, a method was studied for applying a series resonant type fault current limiter that can be manufactured at low cost to the smart grid distribution system. First, the impact of the harmonic components of the short-circuit fault current injected into the series resonance circuit of the fault current limiter on the peak value of the transient response was analyzed, and a methodology for determining the steady-state response was studied using percent impedance-based fault current computation method. Next, the effectiveness of the method was verified by applying it to a test distribution line. The test distribution system using the designed current limiter was modeled using EMTP_RV, and a three-phase short-circuit fault was simulated. In the fault simulation results, it was confirmed that the steady-state response of the fault current accurately followed the design target value after applying the fault current limiter. In addition, by comparing the fault current waveform before and after applying the fault current limiter, it was confirmed that the fault current was greatly suppressed, confirming the effect of applying the series resonance type current limiter to the distribution system.

• Journal of Advanced Navigation Technology
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• v.28 no.2
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• pp.232-237
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• 2024

In this paper, a broadband double dipole quasi-Yagi antenna using a 4×2 meander line array structure for maintaining 8 dBi gain was studied. The 4×2 meanderline array structure consists of a unit cell in the shape of a meanderline conductor, and it was placed above the second dipole antenna of the double dipole quasi-Yagi antenna. A double dipole quasi-Yagi antenna with generally used multiple strip directors was designed on an FR4 substrate with the same size, and the input reflection coefficient and gain characteristics were compared. Comparison results showed that the impedance frequency bandwidth increased by 6.3% compared to when using the multiple strip directors, the frequency bandwidth with a gain of 8 dBi or more increased by 10.1%, and average gain also slightly increased. The frequency band of the fabricated antenna for a voltage standing wave ratio less than 2 was 1.548-2.846 GHz(59.1%), and gain was measured to be more than 8 dBi in the 1.6-2.8 GHz band.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.4
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• pp.641-646
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• 2024

This paper is studied for the design and experiment of a wideband printed 1x2 dipole array antenna for 3.5GHz band application. The printed dipole antenna used in the array antenna was implemented in the form of a rectangular strip, and was consisted with a broadside coupled stripline (BCS). The feed line was designed to be tapered for broadband impedance matching. As a result of comparing the simulation results and measurement results, it was found that the two results were in good agreement with 2.8% error(100MHz shift @3.5GHz). As a result of the experiment, based on VSWR=2, a bandwidth of about 16% was obtained from the center frequency of 3.5 GHz to 3.15~3.70 GHz.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.4165-4170
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• 2012

In this paper, a method for the improvement in the gain and bandwidth of a microstrip-fed broadband planar quasi-Yagi antenna (QYA) is studied. The broadband characteristics of the QYA are achieved from the coplanar strip-fed planar dipole driver and a parasitic director close to the driver. In order to obtain stable gain variation over the required frequency band, a director and a ground reflector are appended to the driver having a nearby parasitic director. The QYA is fed through an integrated balun composed of a microstrip line and a slot line which are terminated in a short circuit. By adjusting the feeding point, a broadband impedance matching is obtained. A QYA with an operating frequency band of 1.75-2.7 GHz and a gain > 4.5 dBi is designed and fabricated on an FR4 substrate with dielectric constant of 4.4 and thickness of 1.6mm. The experimental results show that the fabricated antenna has good performance such as a broad bandwidth of 59.7%(1.55-2.87 GHz), a stable gain between 4.7-6.5 dBi, and a front-to-back ratio > 10 dB. The measured data agree well with the simulation, which validates this study.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.9
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• pp.661-667
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• 2018

Tactical communication radio systems that employ software defined radios(SDRs) have been developed for achieving high-speed data transmissions and voice communications. Such systems possess multiband and multichannel features, and can potentially replace several existing radio systems. This paper proposes a design for wideband antennas by incorporating a diplexer matching network for tactical vehicles. The proposed antenna design includes two radiators(upper and lower) and a diplexer matching network connected to the end of the feed line such that the LC matching networks are interleaved in the lower radiator and spring mount. By employing the diplexer matching network, the designed antenna can perform wideband impedance matching for the fifty ohm feed line. The designed LC networks aid in varying the effective electrical length of the antenna according to the operation frequency. The primary objective behind adjusting the electrical length is to vary the current distribution above and below the LC networks. The proposed antenna was fabricated and tested in an open site. The obtained evaluation results show that the designed antenna can achieve a relative bandwidth of 190% with a VSWR value of 3.5:1, and can attain good antenna gains over VHF and UHF bands.