• Journal of Digital Contents Society
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• v.6 no.2
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• pp.101-106
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• 2005

In this paper, performance evaluation of mobile access layer for multiple-input multiple-output (MIMO) MultiCarrier(MC)/CDMA 16 QAM system is considered to mitigate multiple access interference and enhance system channel capacity in Rayleigh wireless fading channel. Traditionally, multi-path is viewed as an undesirable feature of wireless communications. Therefore, diversity and adaptive array schemes are proposed to mitigate its effects. Recently, to increase the spectrum efficiency and the link reliability, MIMO schemes is devised to exploit multi-path in a scattering wireless channel. In particular, the channel capacity of MIMO-MC/CDMA 16 QAM system is evaluated according to Eb/No, Mc, p. From the results, in order to improve the channel capacity, the signals at various elements must be uncorrelated. And if the paths are correlated due to inappropriate spacing or mutual coupling effects, the channel capacity of MIMO-MC/CDMA 16 QAM system becomes substantially smaller.

• Korean Journal of Optics and Photonics
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• v.3 no.4
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• pp.227-233
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• 1992

The simulation code was developed for the development of the split-disk geometry glass amplifier, which could design the laser apparatus and analyze the properties of the laser system. The flashlamp emission energy at the short wavelength region must be reduced, while maintaining a current density between 2000 and 4000 A/$\textrm{cm}^{2}$, in order to reduce the thermal loading in the laser glass and to raise the coupling efficiency between the emission spectrum of the flashlamps and the absorption spectrum of the laser glass. By cutting the laser glass into three equal pieces, the temperature rise in the laser glass dropped by 70% due to the efficient removal of the heat in the laser glass. It was found that the $Nd^{3+}$ doping rate of each laser glass should be properly selected and the optimum value of the product of the absorption coefficient $\alpha$ and the thickness d of the laser glass is about 0.26 in the split-disk geometry.

• Korean Journal of Optics and Photonics
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• v.19 no.1
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• pp.73-79
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• 2008

We propose a novel metal-waveguide structure for sustaining long-range surface-plasmon-polaritons (LRSPP). The LRSPP waveguides are composed basically of two asymmetric metal layers: a very thin, finite-width metal strip on top of a metal slab with a dielectric gap in between them. Mode cut-off of LRSPPs excited on the double-metal waveguides is characterized by consistently investigating their dispersion relations and mode profiles. We also confirm experimentally the existence of low-loss, well-confined LRSPP modes by measuring far-field outputs emerging from an edge of the asymmetric double-metal waveguides. In the experiment, we have fabricated several types of SPP waveguide devices including straight lines, S-bend, and Y-branch consisting of gold strips (20 nm-thick, $5{\mu}m$-wide). Overall propagation loss of the proposed double-metal waveguides is quite comparable to that of single metal-strip waveguides, in addition the mode sizes can be tuned by increasing the core-insulator gap between the metal layers to get a higher coupling efficiency with a single-mode fiber in telecom wavelength. The proposed LRSPP waveguides may open up realization of SPP-waveguide sensors or nonlinear SPP-devices by replacing the core-insulator with a bio-fluid or a nonlinear medium.

• Korean Journal of Optics and Photonics
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• v.22 no.1
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• pp.5-9
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• 2011

There are technical difficulties in measuring the numerical apertures of multi-mode gradient-index plastic optical fibers (GI-POFs) due to their strong speckle noise originating from dopants, non-uniformity of gradient-index profile, and multi-mode interference. Therefore, we propose a new method of obtaining the numerical aperture by controlling the size of the incident laser beam and measuring the numerical aperture of GI-POF. The results show that we can get a value for the numerical aperture of GI-POF very similar to that measured by the conventional method. We can also obtain the optimum launching condition of input beam and maximum coupling efficiency.

• Korean Journal of Optics and Photonics
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• v.28 no.4
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• pp.135-140
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• 2017

In this paper, we report measured results for an all-fiber $7{\times}1$ pump combiner based on an optical fiber chip for high-power fiber lasers. An optical-fiber chip was fabricated by etching a fiber, having core and cladding diameters of 20 and $400{\mu}m$, in the longitudinal direction. To both ends of the etched chip, we spliced input and output fibers. First, we tied together seven optical fibers, having core and cladding diameters of 105 and $125{\mu}m$ respectively, in a cylindrical bundle and spliced them to the $375-{\mu}m$ end of the optical-fiber chip. Then, we attached an output DCF with core and cladding diameters of 25 and $250{\mu}m$ to the $250-{\mu}m$ end of the optical-fiber chip. Finally, the fabricated $7{\times}1$ pump combiner showed an average optical coupling efficiency of about 90.2% per port. This chip-based pump combiner may replace conventional pump combiners by massive production of fiber chips.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.10
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• pp.17-24
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• 2000

An area efficient and symmetric dual-level spiral inductor structure is proposed and evaluated in comparison with the conventional single-level spiral inductors. Contrary to the dual-level inductor mutual coupling coefficient of the upper-and lower-level inductors of the dual-level inductor increases with the increases in the number of turns. Because of this, for the same silicon area, the inductances of the dual-level incuctors are 2.5-4 times higher than that of the single-level inductor. Furthermore, the dual-level showed better quality factor that the single-level inductors for the same inductance. It is the intention of this paper to demonstrate that the dual-level can be more useful for the RF integrated circuits than the conventional single-level spiral inductors form the aspects of area efficiency and quality factor. The proposed dual-level inductors are designed and confirmed to be perfectly symmetric, and can also be used as a high-frequency choke.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.1
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• pp.35-44
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• 1990

Most of the medium-size ships are powered by large-bore, long-stroke, slow-speed and two-stroke diesel engines in order to improve the fuel efficiency. Such a propulsion plant develops low-frequency excitation forces/moments of significant magnitude. A RO/RO car/truck carrier is also one of the cases. In this paper, the rational methods for analysis of vertical and coupled horizontal-torsional vibrations are presented. Taking account of unusual characteristics of the hull form and structural systems, the emphasis is put on modelling methods based on beam analogy, calculation of system parameters such as added mass and its center, polar added-mass moment of inertia, shear coefficient of hull sections and coupling degree in antisymmetric modes, and modal analysis of forced vibrations.

• Journal of the Korean Data and Information Science Society
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• v.27 no.4
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• pp.887-898
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• 2016

The purpose of this study is to improve the learning ability of probability/statistics for H/W majors. Firstly, we developed a teaching method coupling probability/statistics with programming and multimedia signal processing courses that are opened in the H/W major curriculum. By use of its teaching-learning, we tried to verify the effectiveness on the improvement of learner's academic achievement and then analyze its educational efficiency through the regression analysis. Secondly, by analyzing the surveys and the statistical results of the education cases, we proposed a management plan on efficient teaching-learning in order to cultivate the learning ability of probability/statistics at a future time. Lastly, we concluded that probability/statistics is a required course of learners so as to contribute for the advanced technical development and the enhanced competitiveness in the field of the H/W.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.2
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• pp.149-155
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• 2014

In this paper, we study the complex mobile antenna for WPT(Wireless Power Transfer) with NFC(Near Field Communication) of inductive coupling using FPCB which has half thickness compared with the existing coil type antennas. Considering the pattern thickness of loop antenna, the analysis of electromagnetic wave absorber and battery's influence, absorber thickness, the ranges of design parameters are obtained. The proposed antenna has 0.45 mm thickness using single layer 3 oz FPCB and absorber. From measurement, the characteristics of NFC antenna can be satisfied with the specifications of EMVCo. and domestic mobile telecommunication and the transmission efficiency of the proposed WPT antenna is 68.1 % which is competitive with the existing coil type antenna. From the results of this paper, it has been confirmed that the proposed antenna can be used as the WPT and NFC antenna for mobile phone. Key words: Wireless Power Transfer, Near Field Communication, Mobile Phone Antenna, Absorber, FPCB.

• Journal of electromagnetic engineering and science
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• v.11 no.3
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• pp.166-173
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• 2011

In this paper, we implemented and analyzed a wireless power transfer (WPT) system with a CSPR topology. CSPR refers to constant current source, series resonance circuit topology of a transmitting coil, parallel resonance circuit topology of a receiving coil, and pure resistive loading. The transmitting coil is coupled by a magnetic field to the receiving coil without wire. Although the electromotive force (emf) is small (about 4.5V), the voltage on load resistor is 148V, because a parallel resonance scheme was adopted for the receiving coil. The implemented WPT system is designed to be able to transfer up to 1 kW power and can operate a LED TV. Before the implementation, the EMF reduction mechanism based on the use of ferrite and a metal shield box was confirmed by an EM simulation and we found that the EMF can be suppressed dramatically by using this shield. The operating frequency of the implemented WPT system is 30.7kHz and the air gap between two coils is 150mm. The power transferred to the load resistor is 147W and the real power transfer efficiency is 66.4 %.