• Journal of the Korean Electrochemical Society
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• v.8 no.4
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• pp.181-185
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• 2005

Lithium cobalt oxide thin film cathode, having thickness of $2.9{\mu}m$ with area of $4cm^2$, was deposited on platinum patterned alumina substrate by radio frequency magnetron sputtering. Li/Co molar ratio, which is an important factor for battery performance, was measured as a function of argon working pressure and applied R.F. power. Constant current charge and discharge performances were characterized with high rate discharge and cycling behavior. Using AC impedance analysis, internal resistance of the thin film battery was measured and simulated by proposed equivalent circuit model.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.10
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• pp.1189-1196
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• 2015

In this paper, a microstrip-fed multiband monopole antenna for GPS(Global positioning system)/WiMAX(:Worldwide interoperability for microwave access)/WLAN(Wireless Local Area Networks) for applications was designed, fabricated and measured. The proposed antenna is based on a microstrip-fed structure, and composed of two rectangular double rings and L strips pair and then designed in order to get triple band characteristics. To obtain the optimized parameters, we used the simulator, Ansoft's High Frequency Structure Simulator(HFSS). The proposed antenna is made of $27.0{\times}54.0{\times}1.0mm3$ and is fabricated on the permittivity 4.4 FR-4 substrate. The experiment results shown that the proposed antenna obtained the -10 dB impedance bandwidth 300 MHz (1.325~1.625 GHz), 400 MHz (2.275~2.675 GHz), and 600 MHz (3.15~3.75 GHz) covering the GPS/WiMAX/WLAN bands. Also, the proposed antenna measured gain and radiation patterns characteristics for required operating bands.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.4
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• pp.441-448
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• 2015

In this paper, a CPW-fed dual-band monopole antenna with two branch strips for WLAN(Wireless Local Area Networks) applications was designed, fabricated and measured. The proposed antenna is based on a CPW-feeding structure, and composed of two branch strips and then designed and tuned the length of two branch lines to obtained required frequencies bands. To obtain the optimized parameters, we used the simulator, Ansoft's High Frequency Structure Simulator(HFSS) and carried out simulation about parameters $L_5$, $L_8$, $W_3$, $W_5$, $W_9$. The proposed antenna is fabricated on the FR-4 substrate using the obtained parameters. The numerical and experiment results demonstrated that the proposed antenna obtained the -10 dB impedance bandwidth 1,095 MHz (1.57~2.665 GHz) for 2.4 GHz band and 1,680 MHz (4.99~6.67 GHz) for 5 GHz band satisfied requirement while simultaneously covering the WLAN bands. And characteristics of gain and radiation patterns are determined for WLAN operating bands.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.9
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• pp.841-848
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• 2016

In this paper, a microstrip-fed dual-band monopole antenna with DGS(: Defected Ground System) for WLAN(: Wireless Local Area Networks) applications was designed, fabricated and measured. The proposed antenna is based on a microstrip-fed structure, and composed of two strip lines and DGS structure and then designed in order to get dual band characteristics. We used the simulator, Ansoft's High Frequency Structure Simulator(: HFSS) and carried out simulation about parameters W2, L10, W3, and DGS to get the optimized parameters. The proposed antenna is made of $21.0{\times}36.0{\times}1.6mm3$ and is fabricated on the permittivity 4.4 FR-4 substrate. The experiment results are shown that the proposed antenna obtained the -10 dB impedance bandwidth 700 MHz(2.10~2.80 GHz) and 1,780 MHz(5.02~6.80 GHz) covering the WLAN bands. Also, the measured gain and radiation patterns characteristics of the proposed antenna are presented at required dual-band(2.4GHz band/5.0GHz band), respectively.

• 한국ITS학회:학술대회논문집
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• v.2006 no.10
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• pp.187-190
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• 2006

In this paper, the equivalent circuit of tapped-line that is applied in the feeding of the band-pass filter with high coupling is suggested and the value of an equivalent circuit is mathematically defined. An equivalent circuit of tapped-line is composed by open stub and additional transmission line, and the electrical lengths of stub and line can be obtained by the impedance of resonator and the inverter. The new equivalent circuit of tapped-line can be simply applied of design of band-pass filter and leads to very good agreement compared with theoretical value. The coupled-line band-pass filter using equivalent circuit of tapped-line shows the insertion loss of 1.97 dB and the return loss of 18.5 dB at the center frequency of 5.8 GHz.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11B
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• pp.1612-1619
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• 2001

This paper examines the design, implementation characteristics of a folded dipole active integrated antenna. Our goal was to minimize the physical size of RF circuit and its insertion loss, and to make the high frequency tuning easier by directly integrating the ISM(Industrial Scientific & Medical) band power amplifier and antenna. Non-linear model has been used for highly accurate simulation of the power amplifier. The maximum power level was found by using the Load pull method before an impedance matching was achieved. It is found that the total power-added efficiency(PAE) including the driving amplifier was 31.5% and that the transmit power was 13.7 dBm. We also found that the proposed scheme with the smaller antenna as compared with the existing dipole antenna has 23.7 dB total gain including the antenna gain. The suppression of the second harmonic signal to the fundamental signal with respect to the fundamental signal was found to be more than 30 dBc.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.2
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• pp.207-213
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• 2008

A simplified design procedure for quasi-Yagi antenna arrays using an ultra-wideband balun is presented. The proposed antenna design procedure is based on the simple impedance matching among antenna components: i.e., balun, feed, and antenna This new broadband and high gain antenna array is possible due to the ultra-wideband performance of the balun. As design examples, wideband $1\times4$ and $1\times8$ quasi-Yagi antenna arrays are successfully designed and implemented in Ku-band with frequency bandwidths of about 50 % and antenna gains of 9$\sim$10 dBi and 11$\sim$12 dBi, respectively. And the simulated and measured results demonstrate wide bandwidths and good radiation properties. These antenna arrays can be applied to various phased-array and spatial power combining systems.

• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.999-1010
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• 2003

Uninterrupted power supply has become indispensable during the maintenance task of active electric power lines as a result of today's highly information-oriented society and increasing demand of electric utilities. This maintenance task has the risk of electric shock and the danger of falling from high place. Therefore it is necessary to realize an autonomous robot system using electro-hydraulic manipulators because hydraulic manipulators have the advantage of electric insulation and power/mass density. Meanwhile an electro-hydraulic manipulator using hydraulic actuators has many nonlinear elements, and its parameter fluctuations are greater than those of an electrically driven manipulator. So it is relatively difficult to realize not only stable contact work but also accurate force control for the autonomous assembly tasks using hydraulic manipulators. In this paper, the robust force control of a 6-link electro-hydraulic manipulator system used in the real maintenance task of active electric lines is examined in detail. A nominal model for the system is obtained from experimental frequency responses of the system, and the deviation of the manipulator system from the nominal model is derived by a multiplicative uncertainty. Robust disturbance observers for force control are designed using this information in an H$\_$$\infty$/ framework, and implemented on the two different setups. Experimental results show that highly robust force tracking by a 6-link electro-hydraulic manipulator could be achieved even if the stiffness of environment and the shape of wall change.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.281-284
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• 2006

The resistive V dipole (RVD) is a V antenna with both arms loaded with the continuous Wu-King resistive profile. The RVD has many advantages for surface and subsurface probing, such as the ability to radiate a short pulse in a desired direction. The radiated pulse is simply related to the input pulse, e.g., derivative. In addition, it mostly eliminates the multiple reflections between the surface of the ground and the antenna because of its low radar cross section. The drawbacks of the RVD include the high input impedance and the difficulty in implementation. This paper presents ways to improve the accuracy and easiness of the implementation and to improve the low-frequency performance while maintaining the characteristics of the V antenna that are good for probing applications. The implemented antenna is used to form a bistatic radar to scan targets underground, and the result is imaged.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.1
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• pp.1-5
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• 2000

Co-fired resistors for high frequency MCM-C (Multi Chip Module-Cofired) were fabricated and measured their RF properties from DC to 6 GHz. LTCC (Low Temperature Co-fired Ceramics) substrates with 8 layers were used as the substrates. Resisters and electrodes were printed on the 7th layer and connected to the top layer by via holes. Deviation from DC resistance of the resistors was resulted from the resister pastes, resistor size, and via length. From the experimental results, the suitable equivalent circuit model was adopted with resistor, transmission line, capacitor, and inductor. The characteristic impedance $Z_{o}$ of the transmission line from the equivalent circuit can explain the RF behavior of the buried resistor according to the structural variation.