• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.197.1-197.1
• /
• 2012

위성에서의 전력시스템은 임무를 수행하기 위하여 위성 본체와 탑재체에서 필요로 하는 전력을 생성, 저장, 조절 및 분배하는 역할을 수행한다. 특히, 태양전력 변환장치는 태양전지판에서 생성된 전력을 배터리와 연결된 일차 전력으로의 변환 및 배터리의 충전 제어를 담당한다. 태양전력 변환장치의 동작은 배터리의 특성과 자체 전력 변환 용량에 따라 직접에너지 전달 모드, 최대전력추적 모드, 테이프 모드, 정전압 모드 및 세류 충전 모드로 구분될 수 있다. 본 논문에서는 리튬 이온 배터리를 사용하는 위성에서 직접에너지전달 모드, 최대전력추적 모드 및 정전압 모드를 가지는 태양전력 변환장치에 대한 설계를 기술한다. 설계된 내용을 기반으로 제작된 태양전력변환장치에 대한 궤도상에서의 실제 동작 특성을 분석하여 설계를 검증한다.

• Proceedings of the Optical Society of Korea Conference
• /
• 2003.07a
• /
• pp.208-209
• /
• 2003

고밀도 광집적회로의 광도파로는 단일모드 광섬유와 굴절률의 차이 및 코어 크기에 의해 모드 부정합 문제가 존재한다. 본 논문은 이러한 모드 부정합 문제를 해결할 수 있는 모드 크기 변환기를 설계 하고 3-D Beam Propagation Method (BPM)을 이용하여 분석하였다. 모드 크기 변환기술에는 마이크로 렌즈, 테이퍼 광섬유, 렌즈화 광섬유가 사용되고 있으나 이는 패키징 가격이 높으며 광섬유와의 정렬 문제가 존재하므로, 집적된 실리콘 기판위에 제작하는 모드 크기 변환기에 대한 연구가 다각도에서 시도되고 있다. (중략)

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.12
• /
• pp.1435-1444
• /
• 2008

In this paper, we designed a reduced height waveguide(WG) to microstrip mode converter with a short transition length. The mode converter is composed of a mode converter using E-plane probe and a modified impedance transformer. The mode converter was designed using a probe shorted to top of a 50 ohm ridge WG. The modified impedance transformer was designed to connect the mode converter to the reduced height WG. For wide bandwidth operation, the coupling of the two parts was tuned. The structure of the mode converter was optimized for low loss and wide bandwidth, and the optimized mode converter was fabricated. The performance of the mode converter was extracted using the thru and line S-parameters for back-to-back connections, and the connector loss was calibrated. The mode converter has a right angle structure and short transition length, 7.2 mm. The mode converter shows excellent performances; the insertion loss of 0.12 dB at 15 GHz, and the return loss above 10 dB for the full Ku-band.

• Korean Journal of Optics and Photonics
• /
• v.11 no.2
• /
• pp.119-122
• /
• 2000

We proposed a novel mode shape converter (MSC) that can effectively reduce the coupling loss between polymer rib waveguide and single mode fiber. The double-nb geometry that was used in the novel MSC converted an elliptical mode to circular mode and an circular mode to elliptical mode. This structure can be easily realized by using the typical fabrication process for polymer wavegUide. Simulation using a three dimensional beam propagation method showed that the novel MSC has a coupling loss of 0.079 dB/facet and total lllsertioll loss of less than 0.2 dB. .2 dB.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.42 no.4
• /
• pp.864-870
• /
• 2017

This paper describes a Dual Buck Converter with mode control using variable Frequency to Voltage for portable devices requiring wide load current. The inherent problems of PLL compensation and efficiency degradation in light load current that the conventional hysteretic buck converter has faced have been resolved by using the proposed Dual buck converter which include improved PFM Mode not to require compensation. The proposed mode controller can also improve the difficulty of detecting the load change of the mode controller, which is the main circuit of the conventional dual mode buck converter, and the slow mode switching speed. the proposed mode controller has mode switching time of at least 1.5us. The proposed DC-DC buck converter was implemented by using $0.18{\mu}m$ CMOS process and die size was $1.38mm{\times}1.37mm$. The post simulation results with inductor and capacitor including parasitic elements showed that the proposed circuit received the input of 2.7~3.3V and generated output of 1.2V with the output ripple voltage had the PFM mode of 65mV and 16mV at the fixed switching frequency of 2MHz in hysteretic mode under load currents of 1~500mA. The maximum efficiency of the proposed dual-mode buck converter is 95% at 80mA and is more than 85% efficient under load currents of 1~500mA.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.9 no.1
• /
• pp.39-45
• /
• 2009

OFDM is used for achieving a high-speed data transmission in mobile wireless communication systems. Conventionally, fast Fourier transform that is the main signal processing of OFDM is implemented using digital signal processing. The DSP FFT LSI requires large power consumption. Current-mode FFT LSI with analog signal processing is one of the best solutions for high speed and low power consumption. However, for the operation of current-mode FFT LSI that has the structure of parallel-input and parallel-output, current-mode serial-to-parallel and parallel-to-serial converter are indispensable. We propose a novel current-mode SPC and PSC and full chip simulation results agree with experimental data. The proposed current-mode SPC and PSC promise the wide application of the current-mode analog signal processing in the field of low power wireless communication LSI.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.7 no.3
• /
• pp.246-253
• /
• 1996

In this paper, a problem that occurred in the telegraphist equation established by mode conversion method is solved as analysis tapered transmission line is applied to a waveguide taper. After comparing and analyzing the taper function with variant properties, we select on of taper functions not only that is easily designed but also that have good properties. And then we propose the applicant method to design the waveguide taper and deal with the design of mode transducer between rectangular waveguide and circular waveguide. The measured results of scattering coefficients for the mode transducer fabricated with designed data are agreed well with the theoretical results and the validity of the proposed design and analysis method has been confirmed.

• The Journal of the Acoustical Society of Korea
• /
• v.21 no.7
• /
• pp.600-605
• /
• 2002

In this paper, a Negative Impedance Converter (NIC) circuit was employed for the electro-mechanical characteristic control of a thickness mode piezoelectric vibrator. Two circular plane piezoelectric vibrators were bonded together and the NIC circuit was connected to one of the vibrators. The theoretical and experimental analysis of the characteristics shown that the quality factor and the electro-acoustic efficiency of the vibrator with the NIC circuit could be improved by 20 times and 2.5 times, respectively.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.29 no.2
• /
• pp.93-97
• /
• 2009

An advantage of a magnetostrictive strip transducer for a long-range guided wave inspection is that the wave patterns are relatively clear and simple when compared to a conventional piezoelectric ultrasonic transducer. Therefore, if we can characterize the evolution of defect signals, it could be a promising tool for a structural health monitoring of pipes for a long period of time as well as an identification of flaws. However, when evaluating a signal during a realistic field examination, it should be careful because of some spurious signals or false indications, such as signals due to a directionality, multiple reflections, mode conversion, geometrical reflections etc. Mode converted signals from a realistic piping mockup were acquired and analysed. We found mode conversions between a torsional guided wave T(0,1) mode and a flexural F(1,3) or longitudinal L(0,2) mode generated by a magnetostrictive strip transducer. Based on the experimental observations, an interpretation of the source of the mode conversion is discussed in a viewpoint of electromagnetic properties and structure of the strip transducer.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.41 no.12
• /
• pp.43-49
• /
• 2004

In this paper, we have designed a mode size converter to reduce coupling loss between super-high delta silica optical waveguides and single mode fibers. The new mode size converter has three design aspects; periodically segmented taper waveguide for minimal size, lateral taper waveguide for simple fabrication, and surrounding trenches to improve coupling loss. In the optimal mode size converter design, coupling loss is 0.33dB/point without trenches and 0.2dB/point with trenches.