• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.1
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• pp.14-21
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• 2009

A digital differential transmitter based on CMOS inverter worked up to 2.8 Gbps at the supply voltage of 1 V with a $0.18{\mu}m$ CMOS process. By calibrating the output impedance of the transmitter, the impedance matching between the transmitter output and the transmission line is achieved. The PVT variations of pre-driver are compensated by the calibration of the rising-edge delay and falling-edge delay of the pre-driver outputs. The chip fabricated with a $0.18{\mu}m$ CMOS process, which uses the standard supply voltage of 1.8 V, gives the highest data rate of 4Gbps at the supply voltage of 1.2 V. The proposed calibration schemes improve the eye opening with the voltage margin by 200% and the timing margin by 30%, at 2.8 Gbps and 1 V.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.9
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• pp.1119-1124
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• 2018

So far BESS(Battery Energy storage system) has been widely applied to power systems rapidly. Usually it has been used to regulate the renewable energy output and to adjust the power system frequency. In 2013, EPRI has reported a study of utilizing BESS to replace two black start generators of American Electric Power(AEP) that will be demolished. If the BESS can be used as a self-starting generator, it is possible to shorten the long-distance primary transmission line and shorten the restoration time because BESS is capable of the high-speed start and there is no restriction on the installation position. This paper presents a possibility of using BESS as a self-starting generator by using PSCAD/EMTDC in Korean power systems. Herein, the process to estimated the required capacity of BESS is also presented.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.11
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• pp.902-915
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• 2017

In recent years, mobile devices have become increasingly multi-functional and high performance, resulting in a dramatical increase in processing speed. On the other hand, the size of device is reduced, circuits inside the device are more easily exposed to electromagnetic interference radiated from antenna or adjacent circuits, degrading the system performance. To prevent this, it is necessary to design the device considering the electromagnetic characteristics with EM simulation at the design stage of product. However, the EM simulation takes a long analysis time and require high-level system resources for fast analysis. In this paper, an equivalent circuit modeling method for a round wire is proposed using a PEEC method and the electromagnetic coupling from a dipole antenna to a transmission line is analyzed in frequency domain. And compared with the result of electromagnetic simulator. As a result, PEEC method shows good agreement with those of electromagnetic simulation, in a much more short time.

• Journal of the Institute of Convergence Signal Processing
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• v.14 no.4
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• pp.261-269
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• 2013

This paper describes the design and development of VSI (VLBI standard interface) optical adapter for transmitting VLBI(Very long baseline interferometry) observation data with optical signal. VSI cable comprised of 80-line is being used for observed data transmission with maximum length of 5-meter between playbacks (Mark5B, VERA2000) and raw VLBI data buffer (RVDB), RVDB and VLBI correlation subsystem (VCS) in Daejeon correlator. It has a plan to conduct the data processing for 16-stations and introduce the 14 RVDB systems in near future. And data loss frequently occurred because of trouble of VSI cable MDR80 connector. By considering the data loss by connector error of VSI cable, RVDB system extension plan, effective space usage and long distance data transmission(e-VLBI), the VSI optical adapter was proposed and developed for effectively transmitting and receiving VLBI data through optical signal. In order to confirming the performance of developed VSI optical adapter, the experiments for data transmission was conducted between playback and RVDB system, and confirmed that data transmission was clearly done without any data loss.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.2 no.1
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• pp.20-28
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• 1977

The shipping business which consistutes main stream of foreign trades in the world desires more larger and higher speed ships to convey a large amount of cargo at a time rapidly and safely. They also want to introduce new techniques into transportation system so to meet the rapid growing demand of maritime mobile communications with the improvement of efficiency of radio apparatus and reduction of the hard labors of radio operators mechanization and modernization of radio apparatus is necessary. Now HF band is used mainly for communications between maritime mobile stations and coast stations but the quality of received signal is not so good and the coverage is not sufficient by the condition of propagation of waves. There is also limitation of channel capacity in HF band. So to cope with or improve of these defects and meet the demands of modern maritime communication it is essential to introduce maritime satellite communication system in this field. By using the maritime satellite we can establish high quality communication circuits as maritime Telex, Faximile, high speed data transmission line and can expand coverages. Therefore industrial rationalization of marine transportation is possible with the reduction of painful labors of radio operators by improving safety and promoting of efficiency of movement of ships and freights. Obviously it is prospected that the introduction of maritime satellite communication system will bring a rapid promotion of its usuage in maritime mobile communication field and also anticipated that maritime satellite communication system will be a main current in maritime mobile communication field over the world in the near future with moderated cost of transmission links as in the case of INTELSAT in the past 10 years after its first launching.

• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.127-133
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• 2014

In this paper, we present the design, functions and performance analysis of the virtual machine (VM) based on the Lua interpreter for On-Board Control Procedure Execution Environment (OEE). The development of the OEE has been required in order to operate the lunar explorer mission autonomously which is planned by Korea Aerospace Research Institute (KARI) autonomously. The concept of On-Board Control Procedure (OBCP) is already being applied to the deep space missions with a long propagation delay and a limited data transmission capacity since it ensure he autonomy of the mission without the ground intervention. The interpreter is the execution engine in the VM and it interpreters high-level programming codes line by line and executes the VM instructions. So the execution speed is very more slower than that of natively compiled codes. In order to overcome it, we design and implement OEE using register-based Lua interpreter for execution engine in OEE. We present experimental results on a range of additional hardware configurations such as usages of cache and floating point unit. We expect those to utilized to the OBCP scheduling policy and the system with Lua interpreter.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11B
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• pp.1285-1296
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• 2011

Packet classification is one of the basic and important functions of the Internet routers, and it became more important along with new emerging application programs requiring real-time transmission. Since packet classification should be accomplished in line-speed on each incoming input packet for multiple header fields, it becomes one of the challenges in designing Internet routers. Various packet classification algorithms have been proposed to provide the high-speed packet classification. Hierarchical approach achieves effective packet classification performance by significantly narrowing down the search space whenever a field lookup is completed. However, hierarchical approach involves back-tracking problem. In order to solve the problem, set-pruning trie and grid-of-trie algorithms are proposed. However, the algorithm either causes excessive node duplication or heavy pre-computation. In this paper, we propose a smart set-pruning trie which reduces the number of node duplication in the set-pruning trie by the simple merging of the lower-level tries. Simulation result shows that the proposed trie has the reduced number of copied nodes by 2-8% compared with the set-pruning trie.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.4
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• pp.489-495
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• 2018

In this paper, we designed and fabricated WLAN / UWB communication antennas operating at 3.3 [GHz] and 5 [GHz] bands in order to effectively use the high-speed communication network system that improved antenna miniaturization, gain and radiation pattern. Microstrip patch antennas were chosen to improve the bandwidth. The slot width, length, and transmission line width were calculated using the theoretical formula for each step. Simulation results show that the return loss is -14.053 [dB] at 3.3 [GHz] and -13.118 [dB] at 5 [GHz]. The gain showed a value of 2.479 [dBi] at 3.3 [GHz] and a value of 3.317 [dBi] at 5 [GHz]. After optimizing it with the CST Microwave Studio 2014 program, which can be 3D-designed, Based on these results, we investigated the performance of antennas by measuring their characteristics. In recent years, WLAN, which is a variety of wireless technologies that are continuously developing, and UWB, which is a communication technology which is increasing in frequency band due to an increase in demand of the technology users, is used for a high speed wireless communication system. Communication seems to be possible.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.7
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• pp.817-822
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• 2014

Since the opening of the double-track railway for the Gyeongchun local electric train and the semi-high speed train ITX, floating population between Seoul and Chuncheon has rapidly increased. This is attributable to the competitiveness of the railway service in terms of punctuality and safety of operation, mass transportation and low fare. However, many passengers have expressed strong dissatisfaction and displeasure towards the interior noise and its high rate of increase, particularly in tunnel sections. In this study, the interior noise characteristics of Gyeongchun local electric train and ITX were analyzed and compared. Noise levels, frequency spectrum and sound quality indices were compared for the open land, tunnel and bridge. Finally, from the noise levels depending on the location in the vehicle compartment, the noise transmission path was determined and a basic strategy for reducing the interior noise was developed.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.2
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• pp.19-27
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• 2012

In railway tunnel environment, the reliability of a high-data-rate and real-time train-to-wayside communication should be maintained especially when high-speed train moves along the track. In China and Europe, the communication frequency around 900 MHz is widely used for railway applications. At this carrier frequency band, both of the solutions based on continuously laid leaky coaxial cable (LCX) and discretely installed base-station antennas (BSAs), are applied in tunnel radio coverage. Many available works have concentrated on the radio-wave propagation in tunnels by different kinds of prediction models. Most of them solve this problem as natural propagation in a relatively large hollow waveguide, by neglecting the transmitting/receiving (Tx/Rx) components. However, within such confined areas like railway tunnels especially loaded with train, the complex communication environment becomes an important factor that would affect the quality of the signal transmission. This paper will apply a full-wave numerical method to this case, for considering the BSA or LCX, train antennas and their interacted environments, such as the locomotive body, overhead line for power supply, locomotive pantograph, steel rails, ballastless track, tunnel walls, etc.. Involving finite-difference time-domain (FDTD) method and uni-axial anisotropic perfectly matched layer (UPML) technique, the entire wireless RF downlinks of BSA and LCX to tunnel space to train antenna are precisely modeled (so-called integrative modeling technique, IMT). When exciting the BSA and LCX separately, the field distributions of some cross-sections in a rectangular tunnel are presented. It can be found that the influence of the locomotive body and other tunnel environments is very significant. The field coverage on the locomotive roof plane where the train antennas mounted, seems more homogenous when the side-laying position of the BSA or LCX is much higher. Also, much smoother field coverage solution is achieved by choosing LCX for its characteristic of more homogenous electromagnetic wave radiation.