• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3431-3436
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• 2013

Band-notched ultra-wideband (UWB) antennas using frequency selective surfaces (FSSs) are presented. The proposed antennas utilized the band rejection characteristic of typical FSS unit cells. We loaded the FSS unit cells on the same plane of planar UWB antenna. These antennas are designed to reject the interference from the wireless local area network band, 5.15-5.825 GHz in the UWB band, 3.1-10.6 GHz. The measured peak gains of the proposed antennas are more than 2 dBi at both operation edge and center frequencies, and sufficient to apply for commercial purpose. The antennas are small size and planar shape for the purpose of the small mobile application, and enhanced design freedom by using various existing FSS unit cells.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.10
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• pp.1025-1031
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• 2007

GPS is widely used for positioning applications and attitude of a vehicle can be found also with multiple antennas. However, extremely weak signal level prevents GPS from indoor operation. DR with accelerometers and gyros and landmark based localization method used for indoor applications increase complexity and cost. In this paper, a simple but very efficient ultrasound based attitude determination system which determines both position and attitude in WSN is given. The range between transmitter and receivers are measured using the arrival time difference between ultrasound and RF signal. The 3 dimensional positions can be found using more than 3 range measurements. Furthermore, if more than 2 transmitters are used, the attitude can be determined using the baseline vectors obtained by differencing transmitter and receiver positions. The prototype system is implemented to evaluate the performance of the proposed method. In addition, an error analysis shows the relation between the attitude error and basel me length, quality of measurement and orientation of a vehicle. The static and dynamic experiments performed by micro mobile robot shows accurate position with less than 1.5cm error and attitude with less than 1 degree error can be obtained continuously with 20cm baseline. It is expected that these results can be adapted without modification to indoor applications such as home cleaning robot and autonomous wheelchair maneuvering.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.9 s.351
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• pp.17-22
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• 2006

CMOS LC VCO with fast response adaptive frequency calibration (AFC) technique for IEEE 802.11a/b/g WLANs is designed in 1.8V $0.18{\mu}m$ CMOS process. The possible operation is verified for 5.8GHz band, 5.2GHz band, and 2.4GHz band using the switchable L-C resonators. To linearize its frequency-voltage gain (Kvco), optimized multiple MOS varactor biasing tecknique is used. In order to operate in each band frequency range with reduced VCO gain, 4-bit digitally controlled switched- capacitor bank is used and a wide-range digital logic quadricorrelator (WDLQ) is implemented for fast frequency detector.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.2
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• pp.85-89
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• 2011

In this paper, a novel Class-E power amplifier using metamaterials has been realized with one RF LDMOS diffusion metal-oxide-semiconductor field effect transistor. The CRLH structure can lead to metamaterial transmission line with the Class-E power amplifier tuning capability. The CRLH TL is achieved by the frequency offset and the nonlinear phase slope of the CRLH TL for the matching network of the power amplifier. Also, the proposed power amplifier has been realized by using the CRLH structure in the output matching network for better efficiency. Operating frequencies are chosen at 13.56 MHz in this work. The measured results show that the output power of 39.83 dBm and the gain of 11.83dB was obtained. At this point, we have obtained the power-added efficiency (PAE) of 73 % at operation frequency.

• Journal of IKEEE
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• v.15 no.1
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• pp.15-22
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• 2011

In order to performing the joint operation of Korean army efficiently, informations about surveillance, reconnaissance, and situation awareness need to be possessed jointly. In the first development phase (basis type) of the Korean joint tactical data link system (JTDLS-K), essential tactical information and recognized situation are owned among platforms in common by using existing wireless terminals. In the second development phase (completion type) of the JTDLS-K, a JTDLS which can perform network centric warfare (NCW) will be developed in due consideration of technology development of the basis type and common technology maturity degree. This is a joint battlefield system that can show fighting power simultaneous and polysynthetically through providing command and control messages effectively to each platform, which is participating in the joint and combined operations. In this paper, the development of JTDLS-K with a common data processor based on common link integration processing (CLIP) is described. From the test results of the system presented in this paper, it is demonstrated that quadrature phase shift keying (QPSK) signals can be applied to the system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.115-120
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• 2011

This paper is concerned with the performance comparison of CR-CMA (Coordinate Reduction-CMA) and CM-CMA (Constellation Matching-Constant Modulus Algorithm) that is used for improving the convergence characteristic and residual intersymbol interference which are used as the performance index for an adaptive equalizer. The equalizer is used to reduce the distortion caused by the intersymbol interference on the wireless and the wired band-limited channel, and the blind method which does not need for extra bandwidth by the training sequence of digital code are researched. Recently, by using the merit of simple operation in the CMA, the performance improvement is obtained by the modifying the cost function of it. In this paper, the new algorithm, CR-CMA and CM-CMA, the performance analysis are performed and compared by computer simulation. The CR-CMA has a superior equalization characteristics in the recovered constellation, convergence speed and residual intersymbol interference than the CM-CMA by computer simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.6
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• pp.1049-1056
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• 2016

In this paper, a design method for a compact dual-band slot antenna with bent slot is studied. Bent slots are added on the rectangular slot of the proposed antenna for dual-band operation. The rectangular slot is fed by a coaxial cable by placing a rectangular feeding patch inside the slot. When the bent slots are added onto the both corner of the upper side of the rectangular slot symmetrically, a new resonant frequency is created in low frequency because of the increasement of the slot length. A prototype of the proposed dual-band slot antenna operating at 2.45 GHz WLAN band and 4.50-8.30 GHz band including 5GHz WLAN band is fabricated on an FR4 substrate with a dimension of 30 mm by 30 mm. Experiment results show that the antenna has a desired impedance characteristic with a frequency band of 2.40-2.49 GHz and 4.33-9.85 GHz for an input reflection coefficient < -10 dB.

• Journal of Korea Spatial Information System Society
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• v.10 no.4
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• pp.103-107
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• 2008

This study mainly focused on the development of real-time based damage investigation system using web-GIS. The study area was Gangseo-Gu in Busan where frequently has relatively higher magnitude of damages from natural disasters. GIS DB was built to provide geospatial data such as 1:1,000 and 1:5,000 topographic maps and IKONOS high resolution satellite data. The web-GIS system has demonstrated the higher contribution for the better response and recovery against any type of natural disasters through real-time communication and data dissemination among government agencies and personnel. However, further researches need to be made to improve system capabilities. In addition, for more effective system operation and maximizing the benefits of exploiting web-GIS system, linkage with national DB such as NDMS is essential.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.6 no.1 s.12
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• pp.1-12
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• 2007

The objective of Bus Information System developed as a part of the ITS, provides the operation information of buses to passengers and managers. The system uses roadside antennas (reading electronic tags on board buses) to enable wireless communication each other and radio data communication to deliver information about buses and their locations. This information is used to estimate the arrival time of the bus which will be shown on the bus stop message board or via internet. Bus Information System or Bus Management System (BMS) is going ahead and set up in many local governments, and recently quality improvement of the BIS is considered as a very important element in expanding of business or management. Therefore this research wished to contribute rationalization of the system by maintaining optimum quality. An gang was chosen to apply overall quality control process and will be evaluated in terns of its propriety and performance. This study has led the improvement of service and promote the use of public transits, which is the best way to solve the city traffic problem by effective management of public transits.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.12
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• pp.1113-1119
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• 2013

In this letter, a new approach is proposed for the design of a multi antenna for MIMO wireless devices. The proposed antenna covers various LTE(Long Term Evolution) service bands: band 17(704~746 MHz), band 13(746~787 MHz), band 5(824~894 MHz), and band 8(880~960 MHz). The proposed main antenna consists of a conventional monopole antenna with an inverted L-shaped slit for wideband operation. The proposed the LTE sub antenna is based on a switch loaded loop antenna structure, with a resonance frequency that can be controlled by capacitance of a logic circuit. The tuning technique for the LTE Rx antenna uses a RF MEMS(Micro-Electro mechanical system) to match the impedances to realize the bands of interest. Because the two proposed antennas are polarized orthogonally to each other, the ECC(Envelope Correlation Coefficient) characteristic between two antennas was measured to be very low (below 0.06) with an isolation characteristic below -20 dB between the two antennas in the operating overall LTE bands. The proposed antenna is particularly attractive for mobile devices that integrate LTE multiple systems.