• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.7-17
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• 2006

In this paper, we proposed an optical true time-delay (TTD) for planar phased array antennas (PAAs), which is composed of a wavelength-dependent optical true time delay (WDOTTD) followed by a wavelength-independent optical true time delay (WIOTTD). The WDOTTD is a fiber Bragg gratings (FBGs) Prism and the WDOTTD is a fiber delay-lines matrix of which each component consists of a certain length of fiber connected to cross-ports of a 2${\times}$2 MEMS switch. A 10-GHz 2-bit${\times}$4-bit two-dimensional optical TTD has been fabricated by cascading a WDOTTD with a maximum time delay of 810 ps to a WIOTTD of $\pm$50 ps. Time delay and insertion loss for each radiation angle have been measured. Time delay error for the WIOTTD has been measured to be less than $\pm$1 ps. We have also designed a two-dimensional 10-GHz PAA composed of 8${\times}$8 microstrip patch antenna elements driven by the proposed TTD. The radiation patterns of this PAA have been obtained by simulation and analyzed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.1
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• pp.7-14
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• 2008

In this paper, we propose VATL(Voltage-controlled Artificial Transmission Line) employing periodically loaded diodes for application to on-chip matching components on MMIC. Compared with conventional microstrip line, the VATL showed a much shorter wave length due to periodic capacitance of diodes, and the characteristic impedance of the VATL was easily controlled bγ changing supplied voltage. Concretely, the characteristic impedance of the VATL was changed from $80{\sim}20{\Omega}$ in a range of $0{\sim}1.05V$ and the VATL showed a wavelength of 1.5mm at 20GHz, while conventional microstrip line showed a wavelength of 5.3mm at the same frequency. Using the VATL, a ${\lambda}/4$ impedance transformer was fabricated on GaAs MMIC for application to on-chip matching components on MMIC. Using the ${\lambda}/4$ impedance transformer made it possible to perform impedance matching between RF components with various characteristic impedance of $30{\sim}100{\Omega}$ by adjusting applied Voltage.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.6
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• pp.580-584
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• 1999

The synthesis and characterization of intercalated compound of decansulfonate into hydrated nickel is presented. The compound shows a layered structure as determined by high temperature powder X-ray diffraction (HTXRD). The layer distance of the product is increased from 24.7 $\AA$ to 30.5 $\AA$ by increasing the temperature which is in turn accomplished by changing the structure of the intercalated nickel compound. From the X-ray diffraction data and the decanesulfonate size, the orientation of the decanesulfonate onto the nickel layer is determined. The molecular axis of the decanesulfonate with bilayer structure is tilted to the perpendicular of the nickel layer.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.3
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• pp.360-367
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• 2009

In this paper, the RADANT phase scanning scheme and the transmission-type loaded line phase shifter scheme, which are applicable to the phased array systems, are studied. Using these two schemes, a theoretical method to design an electronic beam steering RADANT lens is introduced. The validity of the presented theoretical method is verified through the simplified circuit simulation results.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.4
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• pp.13-16
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• 1984

This paper proposes a new layout algorithm in order to minimize chip area in one dimensional MOS - LSI composed of basic cells, such as NAND or NOR gates. The virtval gates are constructed, which represent I/O of signal lines at the left-most and at the right-most side of the MCS gate array. With this, a heuristic algorithm is realized that can minimize the number of straight connectors passing through each gate, and as the result, minimize the horizontal tracks necessary to route. The usefulness of the algorithm proposed is shown by the execution of the experimental program on practical logic circuits.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.738-746
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• 1999

In this paper, a microstrip $18\times2$ dual beam array antenna is designed at 10 GHz. The radiating element is an aperture-coupled patch, and it is analyzed by the transmission line model. The feed is a tapered parallel-series type to reduce the side lobe level. To obtain dual beam at $\pm45^{\circ}$, The difference in phase excitation between the elements is $180^{\circ}$. In conclusion, the side lobe level is 25 dB, and the beam width $8^{\circ}$with two main lobes at $\pm44.5^{\circ}$.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.2
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• pp.55-64
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• 2003

Underwater acoustic noise measurement is an essential element for vulnerability assessment of modern naval platforms. But during the last few decades environmental conditions have drastically changed due to the gradually increasing sea ambient noise level and decreasing submarine radiated noise level. A real-time underwater acoustic measurement system with vertical line array is designed for the quiet submarine radiated noise assessment in challenging environment. This system has a constant directivity index in measurement frequency range and accurate tracking capability for the transmission loss compensation and navigation aids inside the submarine. This system has been validated at sea and used several times for the submarine noise measurement.

• The Transactions of the Korea Information Processing Society
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• v.1 no.3
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• pp.409-417
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• 1994

In extracting contours from elevation matrix, the most important problem is to solve the degenerate case where four cross point arise in a grid. This paper describes a technique which performs the checking of degenerate case and determination of next point simultaneously. It requires minimum number of array indexing. Also this paper proposes a technique which reduces the number of array indexing by using LOWER/HIGHER information of a cross point designated according to height difference of grid vertices. In addition, we describe a data structure which is proper for representing cross points and tracing them.

• Polymer(Korea)
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• v.34 no.3
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• pp.242-246
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• 2010

FTIR spectroscopy has been employed in order to quantitatively investigate the relationship between planar arrangements and selective reflectance of cholesteric liquid crystals. It was found that the selective reflection was enhanced as the amount of planar arrangements in cholesteric liquid crystals increased. Although the planar arrangements of cholesteric liquid crystals can be induced only by the shear force effect, it was more effective to use the alignment layer to obtain the perfect planar arrangements.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.4
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• pp.549-554
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• 2017

In this paper, we studied the design and fabrication of $2{\times}2$ microstrip array antenna at around 5 GHz band.. To improve of frequency properties of antenna, feed microstrip patch antenna was simulated by HFSS(High Frequency Structure Simulator). A $2{\times}2$ array antenna was designed and fabricated by photolithograph on an FR4 substrate (dielectric constant of 4.4 and thickness of 1.6 mm). The fabricated $2{\times}2$ array antenna showed a center frequency, the minimum return loss and bandwidth were 5.3 GHz, -24dB, and 390MHz, respectively.