• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.8
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• pp.1297-1304
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• 2000

The full wave method requires a great number of computer memory and lasting long CPU time for the calculation of the discontinuity problems in microstrip structures. While the computation only for the transverse field components at those structures causes the both of time and memory reduction. For the case of the calculating only transverse components for the most of microstrip structures such as low-pass filter, branch coupler and patch antenna the computer memory and running time can be reduced to about 50% and 33%, comparing to the full wave computation. Consequently, the proposed method than that of TEM-mode has an advantages of higher speed and less memory than that of conventional FDTD analysis.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.301-306
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• 2014

We proposed a new PCB-type 'common-mode current($I_c$) and differential-mode current($I_d$) detector' working for fast detection of $I_c$ and $I_d$ from the differential-mode signaling, with miniaturization effect and possibility of cheaper fabrication. In order to realize this device, we suggest a branch-line-coupler balun having a composite right- and left-handed(CRLH) one-layer microstrip phase-shifting line as compact as roughly ${\lambda}_g/14$. The presented balun obviously is different from the conventional bent-&-folded delay lines or slits on the ground for coupling the lines on the top and bottom dielectrics. As we connect the suggested balun output ports of the differential-mode signal lines via the through-port named U and coupled-port named L, $I_c$ and $I_d$ will appear at port ${\Delta}$ and port ${\Sigma}$ of the present device, in order. The validity of the design scheme is verified by the circuit-and numerical electromagnetic analyses, and the dispersion curve proving the metamaterial characteristics of the geometry. Besides, the examples of the $I_c$ and $I_d$ indicator are observed as the even and odd modes in differential-mode signal feeding. Also, the proposed device is shown to be very compact, compared with the conventional structure.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.217-222
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• 2012

Using modal transmission-line theory (MTLT), it explores rigorously the polarization characteristics of plasmonic optical polarizer. To verify the validity of the approach proposed in this paper, a novel polarization condition, which is called mode suppression ratio, is defined. The numerical results reveal that the polarization length of plasmonic optical polarizer is $10{\mu}m$ dramatically shorter than that of conventional dielectric optical polarizer. Furthermore, the insertion loss of plasmonic polarizer consisting of metal Ag is small enough to be neglected below -1dB.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.4
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• pp.297-301
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• 2000

Planar optical waveguides which have a higher refractive index than that of substrate were fabricated by proton exchange between $Li^+$ and $H^+$. Benzoic acid was used as proton source and process was carried out under the various reaction time and temperature. The depth of waveguide layer and the generated mode number were investigated by standard prism coupler. The cut-off depth for the fabrication of single mode optical waveguides was obtained by the function which was expressed on refractive index profile. Finally the experimental conditions for cut-of depth of single mode could be confirmed. Channel waveguides were manufactured from these confirmed conditions and the effective confinement of the induced light into waveguides was observed.

• Korean Journal of Optics and Photonics
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• v.31 no.5
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• pp.213-217
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• 2020

In this study we report a wet-etching-based fabrication method for adiabatic optical-fiber tapers (OFTs), and describe their adiabaticity and HE₁₁ mode evolution at a wavelength of 1550 nm. The profile of the fabricated system satisfies the adiabaticity properties well, and the far-field pattern from the etched OFT shows that the fundamental HE₁₁ mode is maintained without a higher-order mode coupling throughout the tapers. In addition, the measured far-field pattern agrees well with the simulated result. The proposed adiabatic OFTs can be applied to a number of photonic applications, especially fiber-chip packages. Based on the fabricated adiabatic OFT structures, the optical transmission to the inversely tapered silicon waveguide shows large spatial-dimensional tolerances for 1 dB excess loss of ~60 ㎛ (silicon waveguide angle of 1°) and insertion loss of less than 0.4 dB (silicon waveguide angle of 4°), from the numerical simulation. The proposed adiabatic coupler shows the ultrabroadband coupling efficiency over the O- and C-bands.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.12
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• pp.10-15
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• 2013

In this paper, we propose a Lyot-type optical fiber comb filter based on a polarization-diversity loop structure (PDLS), which has flat-top pass bands and multiwavelength switching capability. Generally, the PDLS can remove the dependency of the filter on input polarization. The proposed filter is composed of a polarization beam splitter, two half-wave plates (HWPs), and two polarization-maintaining fiber loops concatenated with a $60^{\circ}$ offset between their principal axes. By controlling two HWPs, it can operate in a flat-top band mode or a lossy flat-top band mode with an inherent insertion loss of ~3.49dB. In particular, flat-top bands can be interleaved in both modes, which cannot be realized in a Lyot-Sagnac comb filter based on a fiber coupler. Compared with Solc-type high-order comb filters with the same order, the proposed filter shows sharper transition between pass and stop bands.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.195-195
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• 2010

In recent years, Anodic aluminum oxide(AAO) has become popular and attractive materials. It can be easily fabricated and self-organized pore structures. It has been widely used as a biosensor membrane, photonic crystal for optical circuit and template for nanotube growth etc. In previous papers, the theory was developed that AAO shows anisotropic optical properties, since it has anisotropic structure with numerous cylindrical pores. It gives rise to the anisotropy of the refractive index called as birefringence. It can be used as conventional polarizing elements with high efficiency and low cost. Therefore, we would like to compare the theory and experimental results in this study. One method which can measure effective refractive index of thin film is the prism coupling technique. It can give accurate results fast and simply. Furthermore, we can also measure separately the refractive index with different polarization using polarization of the laser (TE mode and TM mode). We calculated the effective refractive index with effective medium approximations (EMAs) by pore size in the SEM image. EMAs are physical models that describe the macroscopic system as the homogeneous and typical method of all mean field theories.

• Journal of the Korean Institute of Navigation
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• v.25 no.4
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• pp.455-460
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• 2001

본 연구에서는 방향성 결합기의 특성과 PIN다이오드의 특성을 이용하여 가변 감쇠기를 구현하였다. 기존의 Even-Odd Mode해석법이 아닌 간단한 2-port 기법으로 감쇠기를 분석하였으며, 산란 파라미터는 결합포트의 종단 임피던스가 동일한 경우와 동일하지 않은 경우에 있어서의 감쇠기의 동작특성을 평가하였다. 방향성 결합기의 결합포트는 가변종단을 HP사의 전류제어 소자인 HSMP-3864 PIN다이오드를 사용하였다. 구현된 가변감쇠기는 PCS 송신주파수 1.9 GHz에서 감쇠 범위가 30 dB 이상, 삽입손실 5 dB 이하, 입·출력 반사계수 -25 dB 이하의 특성을 나타내었으며, 이는 PCS와 셀룰러 이동통신 기지국용 전력 증폭기를 온도 등과 같은 외부의 환경변화에 따라서 이득을 가변 시킬 수 있으며, 또한 증폭기의 선형성을 향상시킬 것으로 사료된다.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1841-1843
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• 2001

Asymmetrical parallel coupled lines are used in a number of circuits such as multi-band coupler and combline type band pass filter. Although graphical results and formulas are available for the design of coupled lines, the design procedure is hard to use, because even- and odd- mode impedances are always expressed in terms of the physical geometry. In this paper, we introduce a method to find design parameter using finite element analysis. By employing the capacitance obtained by FE analysis, design parameters for each lines are extracted. To show the validity of extracted design parameter for asymmetrical parallel coupled line, we have designed and simulated a planar type combline band pass filter.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.161-161
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• 2010

In order to achieve low power consumption and the uniform power spectrum of LED BLU (Back Light Unit) system, new circuits with a 2 stage L-C (Inductor-Capacitor) coupler have been proposed. From the simulation results based on our proposed model, the ripple power of the L-C regulation-embedded BLU circuit shows a dramatic reduction by more than 89.3% as compared to the normal BLU (without L-C circuits). This indicates that the proposed circuit is very promising for the realization of high-efficiency BLU circuits.