• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.23-24
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• 2007

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.305-306
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• 2009

This paper shows through detailed simulations that the length of conventionally designed multimode-interference couplers can be shorted significantly by stepped-width and stepped-index design. For the cross-coupling device, this stepped-design results in 9% or more length reduction.

• Korean Journal of Optics and Photonics
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• v.31 no.2
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• pp.105-110
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• 2020

A compact beam combiner based on two-mode interference (TMI) in multimode waveguides is proposed, and its feasibility is shown through simulation with the three-dimensional beam propagation method. The input waveguides are separated by about 1 ㎛ at the interface with the multimode waveguide, so that the fabricated waveguide pattern is well repeated. The power transmission to the output port from the red, green, and blue input port is 93.5%, 94%, and 93%, respectively. When the wavelength deviation from a center wavelength is 10 nm, the power transmission is maintained to be greater than 90%. When the waveguide width error is 40 nm, the power transmission is maintained to be greater than 85% for all the three colors. The polarization dependence of the beam combiner is almost negligible, and its size is as tiny as 0.02 × 4 ㎟.

• Journal of the Korean Geotechnical Society
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• v.29 no.9
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• pp.71-80
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• 2013

This work studies the reliability analysis of a slope that considers multiple failure modes. The analysis consists of two parts. First, significant failure modes that contribute most to system reliability are determined. The so-called barrier method proposed by Der Kiureghian and Dakessian to identify significant failure modes successively is employed. Second, the failure probability for the slope is estimated on the basis of the identified significant failure modes and corresponding design points. For reliability problems entailing multiple design points, failure probability can be estimated by the multi-point first-order reliability method (FORM), Ditlevsen's bounds method, and Monte Carlo simulation. In this paper, a comparative study between these methods has been made through example problems. Analysis results showed that while a soil slope may have a large number of potential slip surfaces, its system failure probability is usually governed by a few significant slip surfaces. Therefore, the most important step in the system reliability analysis for a soil slope is to identify all the significant failure modes in an efficient way.

• Korean Journal of Optics and Photonics
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• v.19 no.1
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• pp.25-30
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• 2008

In this paper, a novel architecture for device miniaturization of multimode interference-based (MMI) couplers is proposed. The coupling length of $N{\times}N$ MMI couplers scales as the square of the MMI region width so that the use of these structures with large-N ports can require large chip size. To solve the design problem, the butterfly grating-assisted MMI couplers, that have smaller device dimensions than conventional MMI couplers, are discussed and evaluated. Numerical simulations and novel design rules for such structures derived through theoretical analysis are presented.

• Journal of IKEEE
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• v.25 no.1
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• pp.218-228
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• 2021

This paper presents the high-efficiency DC-DC converter using the multi-resonant-circuit. The proposed converter has the power topology of half-bridge and utilizes the multi-resonant-circuit that is composed of 2 inductors (LL) and 1 capacitor (C) to achieve high-efficiency. The multi-resonant-circuit forms each resonant circuit of series circuit type with each resonant frequency, according to the operation modes. This paper first describes the operation pirinciples of proposed converter by the operation modes and steady-state fundamental approximation modelling. Then it shows a design example of the proposed converter based on the principles. And it is validated that the proposed converter has the operation characteristics of high-efficiency DC-DC power conversion through the experimental results of prototype converter implemented by the designed circuit parameters.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.2
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• pp.47-52
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• 2013

A novel architecture to reduce dramatically the coupling length of multimode interference-based couplers (MMICs) is proposed by replacing conventionally designed MMICs by cascaded two-section plasmonic stepped MMICs (PS-MMIC). For the 60% cross power splitting ratio in a stepped-width MMIC, the coupling length of device results in around 42% length reduction. Furthermore, the power splitting ratio and coupling length of plasmonic MMIC just vary around 1~2% along the variation of refractive index. On the contrast, those factors for the variation of MMIC's width strongly vary around 30~40%.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.5
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• pp.100-105
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• 2010

A multi-band low noise amplifier (LNA) is designed in 90 nm RF CMOS process for 3GPP LTE (3rd Generation Partner Project Long Term Evolution) applications. The designed multi-band LNA covers the eight frequency bands between 1.85 and 2.8 GHz. A tunable input matching circuit is realized by adopting a switched capacitor array at the LNA input stage for providing optimum performances across the wide operating band. Current steering technique is adopted for the gain control in three steps. The performances of the LNA are verified through post-layout simulations (PLS). The LNA consumes 17 mA at 1.2 V supply voltage. It shows a power gain of 26 at the normal gain mode, and provides much lower gains of 0 and -6.7 in the bypass-I and -II modes, respectively. It achieves a noise figure of 1.78 dB and a IIP3 of -12.8 dBm over the entire band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.5 s.120
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• pp.496-502
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• 2007

In this paper, a slotted waveguide feeder for the electric field uniformity in multi-mode cavity is designed and fabricated. In case of the conventional feeder, a mode stirrer or a turntable is used for improving electric field uniformity in the multi-mode cavity. The proposed feeder has four slots, which have uniform radiation characteristic, on broad wall and shorted terminations at both ends. The electric field uniformity is simulated by CST's MWS(Microwave Studio) for the conventional and proposed feeders, respectively. The fabricated feeder shows the return loss of less than -20 dB at 2.45 GHz. To verify the validity of our proposal, the temperature distribution of the water samples in the multi- mode cavity is observed after a few minutes' heating. The proposed feeder is confirmed to have much better field uniformity in the multi-mode cavity than the conventional feeder.

• 한국정보통신설비학회:학술대회논문집
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• 2002.08a
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• pp.35-38
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• 2002

본 논문에서는 5.8GHz 대역 무선 랜과 차세대 이동통신서비스인 IMT-2000 양 대역에서 동작하는 이중대역 전력증폭기 선계 및 제작에 관하여 기술하였다. 최종 출력목표는 1W이며, 2GHz와 5GHz의 이중밴드로 동작하기 위해 2개의 능동소자를 사용하여, 2개의 독립적인 증폭기를 제작한 후 바이어스 제어회로를 통하여 두 대역을 결합시켰다. 바이어스 제어회로에서 모드 제어 전압 $V_m$의 전압변화에 따라 양 모드간의 변환이 이루어진다.