• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.9
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• pp.1782-1792
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• 1994

Ti : $LiNbO_3$ traveling-wave phase optical modulators at wavelength 1.3㎛ have been designed and fabricated, focusing on the optical waveguide and asymmetric coplanar electrode structure. To improve the phase-mismatch of traveling-wave ACPS electrode, the characteristic impedance, effective microwave index, and electrode loss have been presented as a function of geometric parameters including electrode and buffer layer thickness. Low-loss channel optical waveguides on $LiNbO_3$ were fabricated by the Ti diffusion method with $O_2$ water-vapor environment. $2.5{\mu}m$ thick electrode was successfully fabricated by double-spin image reversal process. Modulation bandwidth was limited by a resonance at 2.9 GHz and modulation bandwidth up to 2.5GHz was approxirnately measured.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.2
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• pp.188-193
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• 2004

In this paper, a microstrip array antenna utilized a subarray with a waveguide slot feeding is presented. This subarray can reduce the feed loss compared with a full microstrip feed network. The subarray has been designed both for a broad reflection bandwidth and a flat gain bandwidth from 40.5 GHz to 43.5 GHz. The 24${\times}$24 series-fed array antenna has been implemented with the maximum gain of 32.4 dBi.

• Journal of the Optical Society of Korea
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• v.19 no.5
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• pp.449-455
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• 2015

In this study we propose a new photonic crystal fiber (PCF) design that simultaneously offers broadband single-mode operation, high birefringence, and large normal dispersion in the optical-communication wavelength regime. The waveguide is based on a hybrid square-lattice PCF (HS-PCF) that has circular air holes of two different diameters alternating in the cladding, plus a pure silica defect at the center. The optical properties of the guided modes are analyzed numerically by the finite-element method (FEM) with a perfectly matched layer as the boundary condition. The optimized HS-PCF has a dispersion coefficient of $-601.67\;ps\;nm^{-1}\;km^{-1}$ and a high birefringence of $1.025{\times}10^{-2}$ at $1.55{\mu}m$. In addition, over the S+C+L+U wavelength bands the proposed HS-PCF with ultraflat birefringence with a slope on the order of $10^{-5}$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.63-64
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• 2017

In this paper, we studied a design method for a coplanar waveguide-fed compact quasi-Yagi antenna for a dual band of the UHF RFID (915 MHz) and GPS (1.575 GHz). The proposed antenna is composed of three elements of a dipole, a reflector, and a director. To reduce its size, the ends of both the dipole and reflector are bent, the director is placed near to the dipole, and a balun is incorporated in the antenna. From some simulations, the proposed antenna using an FR4 substrate with 0.8 mm thickness was designed for the operations in the UHF RFID and GPS systems, and the antenna characteristics such as reflection coefficient, gain, and radiation patterns were examined.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.7
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• pp.75-79
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• 2004

In this paper, a single plane wide band microstrip antenna for integrated circuit as MMIC and LTCC is designed and fabricated. A new configuration for a wide band microstrip antenna with omni-directional pattern is proposed. This antenna consists of two rectangular folded dipoles, which are fed by a coplanar waveguide(CPW). It was effected stabilization ground that a signal plane of CPW feed have been limited ground plane. Therefore, a ground plane of folded structure should be extended outside folded antenna in this research. The characteristics of the proposed antenna were analyzed by using an FDTD methods. The return loss and radiation patterns were simulated and measured. The proposed antenna is get 120MHz bandwidth of PCS band and 250MHz bandwidth of IMT2000 band, used ISM band.

• Korean Journal of Optics and Photonics
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• v.22 no.6
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• pp.256-261
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• 2011

In this paper, a variable optical signal delay line based on coupled ring resonators is designed and fabricated in high-index contrast polymer material. The free spectral ranges (FSR) of the rings are designed to be 100 GHz, and 8 coupled rings are used. When two rings near a bus waveguide are in resonance, the optical delay is measured to be about 100 ps. When four rings are in resonance, the measured delay is about 180 ps. Both are close to the theoretical calculations.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.5
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• pp.38-45
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• 2004

As optical communication is being substituted for telecommunication, the demand of a large variety of fiber optic components is increasing. V-groove substrates, one of the module components, are used to connect optical fibers to optical planar circuits and to arrange fibers. Their applications are multi-channel optical connectors and optical waveguide fiber coupling, etc. Because these substrates are a critical part of the splitter in a multiplexer and a multi fiber connector, precise and reliable fabrication process is required. For precisely aligning core pitch between fibers, machined core pitch tolerance should be within sub-microns. Therefore, these are generally produced by state-of-the-art micro-fabrication like MEMS. However, most of the process equipment is very expensive. It is also difficult to change the process line for custom designs to meet specific requirements using various materials. For various design specifications such as different values of the V angle and low-priced process, the fabrication method should be flexible and low cost. To achieve this goal, we have suggested a miniaturized machine tool with high accuracy positioning system. Through this study, it is shown that this cutting process can be applied to produce V-groove subtracts. We also show the possibility of using a miniaturized machining system for producing small parts.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.453-456
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• 2009

In this paper, a Microstrip antenna for wireless LAN is designed in HyperLAN 5GHz. The IEEE 802.11a have allocated HyperLAN band. We proposed CPW-fed antenna structure for compact antenna. This structure shows that a ground plane and a patch plane are existed at one layer. The proposed antenna is designed on FR-4 substrate with a relative dielectric constant 4.3, thickness of 1.5mm and tangent loss 0.02. The designed antenna shows that VSWR is below 2 and has good return loss below -10dB over the 5.725~5.825GHz bandwidth with HyperLAN.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.1
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• pp.45-51
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• 2009

The propagation characteristics in parallel plate waveguide with dielectric layer having periodic metal strip pattern are investigated. PIN diode ON/OFF states are regarded as the short and open circuit, respectively, in the simulation using CST's MWS. The $11.25^{\circ}$, $22.5^{\circ}$, and $45^{\circ}$ layers which can be used for X-band 4-bit Radant lens phase shifter, are designed. The simulated results for each dielectric layer are $11.28^{\circ}$, $23.2^{\circ}$, and $46.22^{\circ}$, respectively. Also, the equivalent circuit of each layer at the operating band is realized and simulated using Agilent's ADS. The ADS simulated results are compared with the MWS simulated ones. Measured differential phase shills at the center frequency are $9.6^{\circ}$, $22.4^{\circ}$, and $43^{\circ}$, respectively.

• Journal of Advanced Navigation Technology
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• v.19 no.6
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• pp.623-629
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• 2015

In the present study, a coplanar waveguide (CPW)-fed printed monopole antenna with an inverted n-shaped slot is newly proposed for dual band operations which cover bandwidths of CDMA (1.85~2.025 GHz) and WLAN (2.4~2.484 GHz) as well as implementation of omnidirectional radiation pattern. For enhancement of impedance bandwidth ($S11{\leq}10dB$) in 2.4 GHz WLAN frequency band, an inverted n-shaped slot instead of the previous n-shaped slot is etched on the printed radiating monopole. The proposed antenna is designed and fabricated on one side of FR4 substrate with dielectric constant of 4.4, thickness of 1.6 mm, and size of $50{\times}25mm^2$. It has been observed that the measured impedance bandwidths are 280 MHz (1.84~2.12 GHz) in frequency band of CDMA and 420 MHz (2.38~2.8 GHz) in WLAN frequency band respectively. It is noticeable that impedance bandwidth in 2.4 GHz frequency band of WLAN is enlarged to three times due to use of inverted L-shaped slot in comparison with impedance bandwidth 140 MHz (2.39~2.53 GHz) obtained by use of the previous n-shaped slot. In addition, good omnidirectional radiation patterns have been observed over the entire frequency band of interest.