• 한국소프트웨어감정평가학회 논문지
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• 제16권1호
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• pp.55-63
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• 2020

광대역 광통신 시스템에 사용되는 레이저는 우수한 주파수 선택성과 모드 안정성을 가져야한다. DFB(Distributed Feedback) 레이저는 고주파로 전류 변조를 하더라도 발진 주파수의 변화가 적다. 본 연구에서는 1.55um의 파장을 갖는 DFB 레이저에서 굴절률 격자와 이득 격자가 동시에 존재할 때, 오른쪽 거울 면에 반사가 일어나지 않도록 유전막 코팅을 하여 ρ_r=0 이 되도록 하였다. 문턱에서 최소 이득을 필요로 하는 제 1모드에 대하여, 종 방향으로의 발진 모드의 빔 분포와 방사전력비 P_l/P_r를 ρ_l의 위상=π인 경우와 ρ_l의 위상=π/2인 경우에 대하여 비교 검증했다. ρ_l의 위상=π인 경우, 낮은 문턱 전류와 높은 주파수 안정성을 얻기 위해서는, κL이 8보다 커야 한다. ρ_l의 위상=π/2인 경우, 낮은 문턱 전류를 위해서는 κL=1.0이 되도록 해야 하고, 이때 발진 주파수는 격자 주파수와 일치한다. 반사 방지 코팅을 하지 않은, 두 개의 거울 면을 가진 1.55um의 파장을 갖는 DFB 레이저보다, 한쪽 거울 면에 무반사 코팅을 한 경우에 모드 선별성이 훨씬 크다.

• 천문학회보
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• 제42권2호
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• pp.88.1-88.1
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• 2017

We report a novel design of the "linear astigmatism-free" three mirror system (LAF-TMS). In general, the linear astigmatism is one of the most dominant aberration degrading image qualities in common off-axis systems. The proposed LAF-TMS is based on a confocal off-axis three mirror system, where higher order aberrations are minimized via our numerical optimization. The system comprises three pieces of aluminum-alloy freeform mirrors that are feasible to be fabricated with current single-point diamond turning (SPDT) machining technology. The surface figures, dimensions, and positions of mirrors are carefully optimized for a LAF performance. For higher precision-positioning mechanism, we also included alignment parts: shims (for tilting) and L-brackets (for decentering). Any possible mechanical deformation due to assembly process as well as 1-G gravity, and its influence on optical performances of the system are investigated via the finite element (FE) analysis. The LAF-TMS has low f-number and a wide field of view, which is promising for sky monitoring programs such as supernova surveys.

• Journal of Magnetics
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• 제19권3호
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• pp.300-308
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• 2014

This paper develops a moving-magnet electromagnetic actuator for fast steering mirror (FSM). The actuator achieves a reasonable compromise between voice coil actuator and piezoelectric actuator. The stroke of the actuator is between the strokes of a piezoelectric actuator and a voice coil actuator, and its force output is a linear function of air gap and excitation current within our FSM travel range. Additionally, the actuator is more reliable than voice coil actuator as the electrical connection in the actuator is static. Analytically modeling the actuator is difficult and time-consuming. Alternatively, numerous finite element simulations are carried out for the actuator analysis and design. According to the design results, a real prototype of the actuator is fabricated. An experimental test system is then built. Using the test system, the force output of the fabricated actuator is evaluated. The test results validate the actuator analysis and design.

• 대한기계학회논문집
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• 제17권6호
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• pp.1486-1496
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• 1993

본 연구에서는 새로운 연속 전해드레싱 시스템을 구축하고 현재 전자재료로 널리 사용되고 있는 훼라이트에 대하여, 경면연삭을 실현하기 위한 제반 연삭조건 즉, 전해액의 영향, 파크전류와 펄스폭의 영향, 전해드레싱과 취성파괴와의 관계 등을 규명하였다.

• Journal of Magnetics
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• 제19권2호
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• pp.130-139
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• 2014

This paper focuses on the modeling and analysis a novel two-axis rotary normal-stress electromagnetic actuator with compact structure for fast steering mirror (FSM). The actuator has high force density similar to a solenoid, but its torque output is nearly a linear function of both its driving current and rotation angle, showing that the actuator is ideal for FSM. In addition, the actuator is designed with a new cross topology armature and no additional axial force is generated when the actuator works. With flux leakage being involved in the actuator modeling properly, an accurate analytical model of the actuator, which shows the actuator's linear characteristics, is obtained via the commonly used equivalent magnetic circuit method. Finally, numerical simulation is presented to validate the analytical actuator model. It is shown that the analytical results are in a good agreement with the simulation results.

• Journal of Magnetics
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• 제20권1호
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• pp.69-78
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• 2015

This paper focuses on the design of a flux-biased rotary electromagnetic actuator with compact structure for fast steering mirror (FSM). The actuator has high force density and its torque output shows linear dependence on both excitation current and rotation angle. Benefiting from a new electromagnetic topology, no additional axial force is generated and an armature with small moment of inertia is achieved. To improve modeling accuracy, the actuator is modeled with flux leakage taken into account. In order to achieve an FSM with good performance, a design methodology is presented. The methodology aims to achieve a balance between torque output, torque density and required coil magnetomotive force. By using the design methodology, the actuator which will be used to drive our FSM is achieved. The finite element simulation results validate the design results, along with the concept design, magnetic analysis and torque output model.

• Current Optics and Photonics
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• 제6권1호
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• pp.69-78
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• 2022

A high-resolution camera is a precise optical system. Its vibrations during transportation and launch, together with changes in temperature and gravity field in orbit, lead to different degrees of defocus of the camera. Thermal refocusing is one of the solutions to the problems related to in-orbit defocusing, but there are few relevant thermal refocusing mathematical models for systematic analysis and research. Therefore, to further research thermal refocusing systems by using the development of a high-resolution micro-nano satellite (CX6-02) super-resolution camera as an example, we established a thermal refocusing mathematical model based on the thermal elasticity theory on the basis of the secondary mirror position. The detailed design of the thermal refocusing system was carried out under the guidance of the mathematical model. Through optical-mechanical-thermal integration analysis and Zernike polynomial calculation, we found that the data error obtained was about 1%, and deformation in the secondary mirror surface conformed to the optical index, indicating the accuracy and reliability of the thermal refocusing mathematical model. In the final ground test, the thermal vacuum experimental verification data and in-orbit imaging results showed that the thermal refocusing system is consistent with the experimental data, and the performance is stable, which provides theoretical and technical support for the future development of a thermal refocusing space camera.

• 전자공학회논문지C
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• 제34C권11호
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• pp.56-65
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• 1997

In this paper, a design of current-mode continuous-time filters for low voltage and high frequency applictions using complementary bipolar current mirror paris is presented. The proposed current-mode filters consist of simple bipolar current mirrors and capacitors and are quite suitable for monolithic integrtion. Since the design method of the proposed curent-mode filters is based on the integrator type of realization, it can be used for a wide range of applications. And the cutoff frequency of th efilters can be easily changed by the DC cntrolling current. As design examples, the 5th order butterworth filters are designed by cascade and leapfrog methods with tunable cutoff frequencies from 30MHz to 100MHz. The characteristics of the designed current mode filters are simulated and examined by SPICE using standard bipolar transistor parameters.

• 전자공학회논문지D
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• 제36D권6호
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• pp.35-43
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• 1999

본 논문에서는 자유 공간 광 연결 구도에 적합한 새로운 구조의 광 thyristor를 제안하고, 이 소자의 성능을 기존의 광 thyristor와 비교 평가하였다. 제안된 광 thyristor는 얇은 가운데 층들을 갖는 완전 공핍 광 thyristor로서 빠른 스위칭 속도와 향상된 광 반응성을 위하여 다중 양자 우물(multiple quantum wells)과 하부 거울층(bottom mirror)을 이용하였다. 기존 광 thyristor와의 성능 비교를 위한 모의실험은 전류 중심(current oriented) 연결 접합 모델(coupled junction model)과 박막층의 특성 행렬(thin film characteristic matrix), 그리고 van Roosbroeck-Shockley relation을 이용하였다. 모의 실험을 통하여 소자의 구성 물질, 두께, 불순물 농도등의 물리적 인자들이 같은 경우, 기존의 광 thyristor에 비하여 제안된 광 thyristor의 스위칭 에너지가 0.43 배 줄고, 발광 효율은 1.76 배 증가하며, 연동 동작(cascadable operation)시 bit-rate는 1.61 배 증가함을 알 수 있었다.

• 한국전자통신학회논문지
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• 제14권6호
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• pp.1145-1152
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• 2019

본 논문에서는 디지털 회로와 저소비전력 및 고속연산의 장점을 가진 아날로그 회로를 혼용하기 위하여, 저전력 전류모드 12비트 ADC(: Analog to Digital Converter)를 제안하였다. 제안하는 12비트 ADC는 4비트 ADC의 cascade 구조를 사용하여 소비전력을 줄일 수 있었으며, 변환 current mirror 회로를 사용해 칩면적을 줄일 수 있었다. 제안된 ADC는 매그나칩/SK하이닉스 350nm 공정으로 구현하였고, Cadence MMSIM을 사용하여 post-layout simulation를 진행하였다. 전원전압 3.3V에서 동작하고, 면적은 318㎛ x 514㎛를 차지하였다. 또한 제안하는 ADC는 평균 소비전력 3.4mW의 저소비전력으로 동작하는 가능성을 나타내었다.