• Journal of Advanced Navigation Technology
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• v.5 no.2
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• pp.158-164
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• 2001

We presented a channel model for the inter vehicle radio link including the reflection from the road surface, side road vehicle and concrete wall. Then we theoretically derived the path loss and delay profile characteristics using the Ray tracing method efficiently analyzing millimeter wave or optic wave. Finally, we shown the improvement of propagation characteristics by diversity techniques, BCH coding and convolution coding techniques. At the result, MRC diversity techniques and BCH coding can't obtained PER = $10^{-6}$ which is considered to be data service criterion. But, we knew that Packet Error Rate Characteristic can obtained PER = $10^{-6}$, which is considered to be data service criterion, when convolution coding scheme are adopted in Rician fading.

• The KIPS Transactions:PartC
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• v.12C no.1 s.97
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• pp.77-82
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• 2005

Protection of user service becomes increasingly important since even very short interruption of service due to link or node failure will cause huge data loss and incur tremendous restoration cost in high speed network environment. Thus fast and efficient protection and restoration is one of the most important issues to be addressed. Protection methods have been proposed to provide efficiency and stability in optical networks. In this paper, an original network is separated into several domains using Hamiltonian cycle. and link protection is performed on the cycles of the domains. We have shown that protection path length can be decreased up to $57{\%}$ with marginal increase of backup capacity. Our proposed method can provide high-speed protection with marginal increase of protection capacity.

• The KIPS Transactions:PartC
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• v.13C no.6 s.109
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• pp.749-756
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• 2006

Broadcast nature of wireless medium and path-loss reduction create a favourable condition for collaborative communications (CC) among single-antenna users to gain the powerful benefits of multi-antenna system without the demand for physical arrays. This paper proposes a CC strategy adapting to the propagation environment changes by optimizing the transmit signal amplification factors to simplify the structure of maximum likelihood (ML) detector and to obtain the minimum error probability as well. The closed-form BER expression was also derived and compared to the simulation results to evaluate the performance of the suggested solution. A variety of numerical results revealed the cooperation significantly outperforms non-cooperative counterpart under flat Rayleigh fading channel plus AWGN (Additive White Gaussian Noise).

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.537-540
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• 2000

The Distribution System consist of many tie-line switches and sectionalizing switches, operated a radial type. When an outage occurs in Distribution System, outage areas are isolated by system switches, has to restored as soon as possible. At this time, system operator have to get a information about network topology for service restoration of outage areas. Therefore, the searching result of restorative topology has to fast computation time and reliable result topology for to restore a electric service to outage areas, equal to optimal switching operation problem. So, the problem can be defined as combinatorial optimization problem. The service restoration problem is so important problem which have outage area minimization, outage loss minimization. Many researcher is applying to the service restoration problem with various techniques. In this paper, advanced Dijkstra algorithm is applied to searching a restoration topology, is so efficient to searching a shortest path in graph type network. Additionally, fuzzy rules and operator are applied to overcome a fuzziness of correlation with input data. The present technique has superior results which are fast computation time and searching results than previous researches, demonstrated by example distribution model system which has 3 feeders, 26 buses. For a application capability to real distribution system, additionally demonstrated by real distribution system of KEPCO(Korea Electric Power Corporation) which has 8 feeders and 140 buses.

• Proceedings of the KSRS Conference
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• v.1
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• pp.204-207
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• 2006

COMS will receive two different meteorological signals in S-Band from IDACS (Image Data Acquisition and Control System) in ground station before transmitting them in L-Band to user station. MODCS (Meteorological Ocean Data Communication Subsystem) in satellite released the value of required PFD (Power Flux Density) to receive two signals. Thus, DATS (Data Acquisition and Transmission Subsystem) needs to send two signals to satellite with a satisfied EIRP. The value of minimum HPA (High Power Amplifier) output power was estimated by subtracting antenna directional gain and path loss between antenna and HPA from the needed EIRP in this paper. Besides the minimum output power of HPA, the maximum output power was also calculated with considering IMD (Inter-Modulation Distortion) characteristics. IMD is always occurred in the output of HPA when LRIT and HRIT are amplified by using single HPA as COMS application. In this paper, the setting of maximum output power was determined when the IMD of modelled HPA was corresponded to the requirement of MODCS.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.239.1-239.1
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• 2011

Dye sensitized solar cells (DSC) are promising devices for inexpensive, nontoxic, transparent, and large-scale solar energy conversion. Generally thick $TiO_2$ nanoporous films act as efficient photoanodes with their large surface area for absorbing light. However, electron transport through nanoparticle networks causes the slowdown and the loss of electron transport because of a number of interparticle boundaries inside the conduction path. We have studied DSCs with precisely dimension-controlled $TiO_2$ nanotubes array as photoanode. $TiO_2$ nanotubes array is prepared by template-directed fabrication method with atomic layer deposition. Well-ordered nanotubes array provides not only large surface area for light absorbing but also direct pathway for electrons with minimalized grain boundaries. Large enlongated anatase grains in the nanotubes could enhance the conductivity of electrons, but also suppress the recombination with holes through defect sites during diffusion into the electrode. To study the effect of grain boundaries, we fabricated two kinds of nanotubes which have different grain sizes by controlling deposition conditions. And we studied electron conduction through two kinds of nanotubes with different grain structures. The solar cell performance was studied as a function of thickness and grain structures. And overall solar-to-electric energy conversion efficiencies of up to 7% were obtained.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.954-960
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• 2009

In this paper, Indoor Positioning System based on Wi-Fi system which is one of the key technology in LBS(Location Based Service) is proposed. The proposed system estimates distance between MS(Mobile Station) and AP(Access Point) using RSSI(Received Signal Strength Indicator). RSSI is affected by outlier that originate from indoor environment complexity and obstacle. In this paper, we introduce a Robust outlier Extended Kalman Filter that can ignore, real-time outlier in the observations. To demonstrate performance of proposed indoor positioning system, we used a PDA as the MS.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.4
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• pp.452-459
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• 2009

A 6-bit MMIC digital attenuator applicable to X-band TR module has been developed by using $0.5{\mu}m$GaAs pHEMT processes. The Switched-T attenuator scheme and the switched-path attenuator scheme were adopted to obtain low insertion loss and small phase variation, respectively. Resistors and transmission lines are optimized to achieve the digital attenuator with high attenuation accuracy and small phase variation. The digital attenuator has RMS error of 0.4dB, resolution of 0.5dB and dynamic range of 31.5dB. The measurement results show that in-out VSWRs are less than 1.5, phase variation is from -7 to +2 degrees and IIP3 is 36.5dBm.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.3
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• pp.107-115
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• 2003

This paper deals with the effect of the auxiliary pole core in the automotive starter motor on its characteristics. This motor is excited by the permanent magnet and has auxiliary pole core in the stator. The auxiliary pole core is a device to increase the effective flux to obtain the starling torque and prevent the demagnetization of the permanent magnet from the starting current. It Is important to design the auxiliary pore core. And overhang structure causes the electromagnetic phenomenon of 3-dimensional flux Path. Therefore. the characteristic analysis is achieved by the 2-dimensional Finite Element Method (FEM) with the compensated model and the 3-dimensional Equivalent Magnet Circuit Network (3D EMCN). The mechanical loss and the brush and coil resistance are separated from the various experiment of the tested motor, and then these factor are reflected on the analysis results. The validity of the proposed analysis method is verified by comparing the experimental and analysis results. The effects of the design parameters related to the auxiliary pole cote on the motor performance are analyzed by the proposed method.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.4
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• pp.5-8
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• 2009

In this paper, a high-quality low-temperature co-fired ceramic (LTCC) solenoid inductor using a solder ball and an air cavity on a silicon wafer for three-dimensional (3-D) system-in-package (SiP) is proposed. The LTCC multi-layer solenoid inductor is attached using Ag paste and solder ball on a silicon wafer with the air cavity structure. The air cavity is formed on a silicon wafer through an anisotropic wet-etching technology and is able to isolate the LTCC dielectric loss which is equivalent to a low k material effect. The electrical coupling between the metal layer and the LTCC dielectric layer is decreased by adopting the air cavity. The LTCC solenoid inductor using the solder ball and the air cavity on silicon wafer has an improved Q factor and self-resonant frequency (SRF) by reducing the LTCC dielectric resistance and parasitic capacitance. Also, 3-D device stacking technologies provide an effective path to the miniaturization of electronic systems.