• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.1
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• pp.1-8
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• 2014

Using the level set and the meshfree methods, we develop a topological shape optimization method applied to linear elasticity problems. Design gradients are computed using an efficient adjoint design sensitivity analysis(DSA) method. The boundaries are represented by an implicit moving boundary(IMB) embedded in the level set function obtainable from the "Hamilton-Jacobi type" equation with the "Up-wind scheme". Then, using the implicit function, explicit boundaries are generated to obtain the response and sensitivity of the structures. Global nodal shape function derived on a basis of the reproducing kernel(RK) method is employed to discretize the displacement field in the governing continuum equation. Thus, the material points can be located everywhere in the continuum domain, which enables to generate the explicit boundaries and leads to a precise design result. The developed method defines a Lagrangian functional for the constrained optimization. It minimizes the compliance, satisfying the constraint of allowable volume through the variations of boundary. During the optimization, the velocity to integrate the Hamilton-Jacobi equation is obtained from the optimality condition for the Lagrangian functional. Compared with the conventional shape optimization method, the developed one can easily represent the topological shape variations.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.2014-2016
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• 2004

In order to obtain a low-loss ferroelectric phase shifter, the reflection-type phase shifter with ferroelectric defected ground structure (DGS) resonators has been designed in this paper. The proposed phase shifter is consist of a 3-dB $90^{\circ}$ branch-line hybrid coupler and terminated reflective circuit with tunable ferroelectric DGS resonator. The ferroelectric DGS unit structure can provide high Q resonator characteristic at high frequencies. The design parameters of equivalent circuit for the tunable DGS resonator are derived by using simple circuit analysis method and three-dimensional full wave finite element method. The fabricated phase shifter has an insertion loss of better than 3.4dB at 13.5GHz.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.11
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• pp.1-9
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• 2003

The electromagnectic modal analysis method for the multiscreen structure with periodic slot array with including conductor thickness effect is presented. The multiscreen structure is seen to be exactly equivalent to a microwave guide closed by phase-shift walls. From this viewpoint, the entire generalized scattering matrix of the multiscreen structure is calculated by the cascade connection of the scattering matrices obtained by the modal analysis at guide junctions and the transmission matrices of guide region. The present method is verified in comparison with the results calculated by the previous method of moment for single screen structure. As an application example of the present method, the spatial filter having multiscreen structure is designed and the interesting characteristics such as transmission and reflection coefficient versus frequency & angle are investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.193-193
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• 2009

Thin-type 초음파모터의 구조는 크로스형태의 앓은 스테이터에 윗면과 아랫면에 각각 8개의 압전세라믹이 부착된 형태이고, 압전세라믹의 분극방향은 로터와 접촉하는 스테이터의 중심부인 네 개의 타점에서 순차적인 타원변위가 생성되도록 결정된다. 유한요소해석프로그램인 ATILA 5.2.4를 사용하여 형태, 길이, 두께, 스테이터 재질, 클램프특성이 최적 설계된 모델을 제작하였고, 푸쉬풀 게이지, x-y 스테이지, rpm 메터, 토크 게이지, 맨코더, AD컨버터를 이용하여 피드백 제어 구동시스템을 구성하였다. 그림 I은 마이크로컨트롤러 (ATmega)와 피드백회로를 이용한 구동 드라이버를 보여준다. 한 주기에서 1/4분주의 순차적인 네 개의 구형파를 생성하고, 이를 push-pull회로를 통하여 90도의 위상차가 나는 정현파를 생성하여 초음파 모터의 구동전원으로 사용한다. 피드백 회로인 엔코더와 AD 컨버터는 초음파모터의 속도를 피드백하여 정속도 운전을 위한 전압제어에 사용되었다. 특성 측정 결과, 제품화된 드라이버와 비교하여 큰 차이를 보이지 않았고 피드백 회로를 통하여 부하변화에 따른 속도의 극심한 변화를 0.2~0.4[N]의 범위에서 정속도 운전이 가능하였으며, 장시간의 운전에도 온도 및 속도특성이 안정적임을 확인하였다.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.2 no.1
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• pp.30-36
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• 2003

Recently, mechanically beam-steering microstrip patch array antenna using MEMS technology is developed and tested. In this paper as an application of developed antenna, new radiation pattern synthesis method far beam-steering antenna without phase-shifter is proposed, and applied to synthesis of desired beam shape. Niching genetic algorithm using Restricted Competition Selection (RCS) is used for radiation pattern optimization. This approach can be applied to design of array antenna for meet EMC standard and through proposed method specific beam shapes can be synthesized.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.3
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• pp.371-375
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• 2014

In this paper, we compared the performances of the Right Handed Transmission Line (RHTL) and the Left Handed Transmission Line (LHTL) phase shifters as a frequency translator. Unlike other phase shifters, both phase shifters show a $0^{\circ}-360^{\circ}$ phase variation for a broadband frequency and compact in size which are ideal to use as a frequency translator. For the performance comparison, we fabricated both a RHTL and a LHTL phase shifter to cover 1.5 GHz - 2.4 GHz range with the whole $360^{\circ}$ phase variation. For the frequency range, a LHTL based frequency translator showed a much better performance whose Spurious Free Dynamic Range (SFDR) is 4dB - 17dB higher than the RHTL based frequency translator when the sawtooth modulation freqncy is 11 kHz. This is due to the linear phase-voltage variation of LHTL phase shifter. Furthermore, the LHTL phase shifter shows a less insertion loss and a insertion loss variation than the RHTL phase shifter. Overall, the LHTL based frequency translator outperformed RHTL based freqency translator.

• Journal of Advanced Navigation Technology
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• v.13 no.2
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• pp.187-193
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• 2009

A lens which is one of cores for the high precision laser range finder is utilized to compute the distance by measuring the phase displacement. In order to measure the phase displacement, we transmit the optical signal from the laser diode to a target and receive the reflected laser light from the target. In this paper, we propose new lens design technique to solve the problem due to the inconsistent curvature of the lens, which consistently collects optical signals and performs the transmission and reception of the optical data, and test the implementation of the laser range finder based on the proposed technique. Since the proposed laser range finder has low error rate comparing to the conventional techniques, it may be apply to the high precision distance measurement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.10
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• pp.4685-4693
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• 2013

Present work deals with a shape optimal design to minimize the weight of the mask-frame used in the process of OLED vapor deposition by the fine metal mask. A design concept for an optimal shape of the frame to increase the stiffness and to reduce the weight is derived using the topology optimization, shape design variables of the frame by adopting slots being defined. An optimal shape is determined by solving the shape optimization problem to minimize the weight of the frame under constraints of the maximum displacement. Weight of the optimal design is 117.6 kg, which is reduced by 138.4 kg(54.1%) of that of the first design, 256 kg.

• 한국정보통신설비학회:학술대회논문집
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• 2003.08a
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• pp.286-288
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• 2003

In this paper, in order to obtain a large differential phase shift with a little change in applied voltage, a ferroelectric reflective load circuit has been designed on top of barium strontium titanate $(Ba,Sr)TiO_3$ [BST] thin film. The design of the ferroelectric reflection-type phase shifter is based on a reflection theory of terminating circuit, which has a reflection-type analogue phase shifter with two ports terminated in symmetric phase-controllable reflective networks. To achieve large amounts of phase shift in low bias-voltage range, the effects of change of capacitance and transmission line connected with two coupled ports of a 3-dB $90^{\circ}$ branch-line hybrid coupler have been investigated. A large phase shift with a small capacitance change in the parallel terminating circuit has been demonstrated in the paper.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.616-619
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• 2003

This work presents the design, fabrication and microwave performance of distributed analog phase shifter (DAPS) fabricated on $(Ba,\;Sr)TiO_3$ (BST) thin films for X-band applications. Ferroelectric BST thin films were deposited on MgO substrates by pulsed laser deposition. The DAPS consists of high impedance coplanar waveguide (CPW) and periodically loaded tunable BST interdigitated capacitors (IDC). In order to reduce the insertion loss of DAPS and to remove the alteration of unloaded CPW properties according to an applied dc bias voltage, BST layer under transmission lines were removed by photolithography and RF-ion milling. The measured results are in good agreement with the simulated results at the frequencies of interest. The measured differential phase shift based on BST thin films was $24^{\circ}$ and the insertion loss decreased from 1.1 dB to 0.7 dB with increasing the bias voltage from 0 to 40V at 10 GHz.