• 한국정보통신설비학회:학술대회논문집
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• 2004.08a
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• pp.153-156
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• 2004

광 전송 마이크로 셀룰라 시스템과 부반송파 다중 송신 시스템 같은 마이크로파 광 전송기술을 이용한 시스템들은 송신기의 비선형성에 의해서 발생하는 많은 왜곡 성분들, 특히 레이저 다이오드에서 발생한 왜곡 성분들에 의해서 많은 성능의 제한을 받는다. 이러한 왜곡 성분들을 제거하기 위해서 광 피드포워드 방식을 이용한 광 송신기를 제안하였다. 제작된 피드포워드 선형화 아날로그 광 송신기는 2.1 GHz 투톤 실험에서 38 dB의 IMD 개선 효과를 보였다. 여기에서 위상 천이기와 전압 가변 감쇄기는 신호 크기 허용오차를 0.1 dB, 위상 허용오차 $1^{\circ}$범위 이내에서 설계하였다. 이를 위해서 세밀한 위상과 크기의 조정이 가능한 위상 천이기와 전압 가변 감쇄기를 제작하였고, 측정한 결과, 전압 가변에 따른 위상 변화량과 크기 변화량은 각각 위상 천이기는 $90^{\circ}$, 전압 가변 감쇄기는 14 dB를 기록하였다.

• Aerospace Engineering and Technology
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• v.13 no.2
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• pp.73-79
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• 2014

During developing cubesat flight software, Communication test between cubesat and ground station is needed. For this, we have constructed indoor ground station without outdoor antenna for decreasing total cost and time. In this time, if output power of ground station is high, it will affect for cubesat transceiver to be fail. For solving this problem, ground station must be designed for output power of it to be lower than input power of cubesat satellite, and it must be verified. In this paper, first, we describe cubesat indoor ground station using UHF and VHF. Second, we describe output power decreasing test for indoor operation of ground station by attaching attenuators in the end of the output connector.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4A
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• pp.458-465
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• 2004

To reaffirm the use of a mainstream CMOS process for designing passive-like attenuator structures, a linearly controlled variable attenuator is realized with 0.35${\mu}{\textrm}{m}$ 2-poly 4-metal CMOS process. It uses the П configuration for large attenuation range and suitable matching property. Compared to conventional passive-like CMOS attenuators, it is demonstrated that this work advances the frequency band from MHz to ㎓ (DC- l㎓), and reduces the size to 700${\mu}{\textrm}{m}$${\times}$300${\mu}{\textrm}{m}$.. Both simulation results and test results are provided. They show the improved linear relation between attenuation and control voltage. It is very useful in CDMA or GSM band, which uses under 1㎓ frequency band. An alternative topology, Bridged-T configuration, is proposed to get over the limit of applications by elevating operation bandwidth. The proposed topology covers over DC-2㎓ frequency band, which means that the proposed architecture can cover the tripleband (800MHz CDMA/GSM, 1.5㎓ GPS, 1.9㎓z PCS system) in applications as well. The simulation results are provided.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.309-312
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• 2003

본 논문에서는 유전체 기판형태에서 대역통과 여파기의 크기를 줄이며, 감쇄극을 통과대역 양쪽에 적절하게 위치시키어 감쇄특성을 개선시킬 수 있는 구조를 제안한다. 제시된 구조는 일반적인 헤어핀구조와 접지면에 슬롯라인을 구현해주어 2단 대역통과 여파기를 설계하였다. 설계된 대역 여파기의 등가회로를 제시하였고 시뮬레이션 및 측정 결과를 비교하였다. 구현된 여파기는 일반적인 결합선로 여파기에 비해 크기를 크게 줄 일수 있었고, 감쇄특성은 3단 대역통과 여파기의 감쇄특성에 비교할 수 있다. 제시된 구조는 소형화 및 성능개선에 장점을 가지고 있어 다른 소자에도 많은 적용이 가능할 것으로 생각된다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5A
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• pp.566-573
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• 2004

A variable optical attenuator with a bending-sensitive fiber (BSF) that can be used in optical networks is developed. The proposed BSF consists of inner core, outer core, center dip and cladding. The proposed BSF is also very sensitive to mechanical perturbation, such as bending and pressure, making the light propagating in the BSF easily controlled and attenuated. The fabricated fiber-type variable optical attenuator using the proposed BSF (VOAFB) consisted of the BSF in a rectangular rubber ring with a fixed bend radius (BR) in a steady state. The variable optical attenuator using the proposed BSF (VOAFB) was able to attenuate the optical power by more than about -38㏈ with the gradient -88.4［㏈$.$$cm^{-1}$ /］ at (1540∼1560nm) based m adjusting the mechanical pressure applied to the upper surface of the rectangular rubber ring with the bent BSF. According to the experimental results when using the proposed VOAFB, the optical power was easily controlled by adjusting mechanical pressure and produced an insertion loss of 0.68㏈, polarization loss of 0.5㏈, and return loss of less than -60㏈.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.12-16
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• 2003

This paper presents a compensation method for a temperature-dependent gain tilt in L-band erbium-doped fiber amplifier using a voltage-controlled attenuator. The gain tilts in the L-band of 1570-1605 nm due to a temperature change have negative slopes, whereas they have positive slopes for the increasing optical input powers in a saturation region. The proposed method utilizes these opposite gain variations to compensate for the gain tilt over a wide range of temperature. While applying forty channels with a channel spacing of 100 GHz in the L-band and changing the ambient temperature from 0 to $50^{\circ}C$, the compensation method maintained the gain deviation within 1 dB.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.202-205
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• 2000

본 논문에서는 IMT-2000용 고전력 중폭기에 사용할수 있근 전치 왜곡기를 feedback 방식을 이용하여 설계하였다. 여기서 feedback 방식을 사용함으로써 기존의 전치 왜곡기와는 달리 증폭기의 이득을 조절하기 위해 감쇄기를 사용하지 않고 feedback에 사용한 저항값을 사용하여 이득을 조절하도록 설계하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.5
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• pp.443-450
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• 2000

A PWM inverter for an induction motor often has a problem with a high frequency leakage current that flows through stray capacitors between stator windings and a motor frame to ground. This paper proposes a new type of Active Common Mode Voltage Canceler circuit for the reduction of common mode voltage and high frequency leakage current generated by the PWM VSI-fed induction motor drives. The compensating voltage applied by the common made voltage canceler has the same amplitude as, hut the opposite polarity to, the common mode voltage by PWM Inverter. Therefore, common mode voltage and high frequency leakage current can be canceled. The proposed circuit consists of four-level half-bridge inverter and common-mode transformer. Simulated and experimental results show that common mode voltage canceler makes significant contributions to reducing a high frequency leakage current.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.4
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• pp.55-60
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• 1999

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1998.10a
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• pp.776-779
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• 1998