• 한국음향학회지
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• 제18권1호
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• pp.16-24
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• 1999

사다리형 SAW 필터의 개발을 위해서 종래에는 설계변수 하나하나를 변화시켜 시행착오식으로 사양을 만족시키는 값을 찾아야만 하였다. 본 연구에서는 주어진 사양을 만족시킬 수 있는 사다리형 SAW 필터의 패턴을 자동으로 설계하는 최적 설계법을 개발하였다. 우선 Smith 등가회로 해석법을 이용하여 사다리형 SAW 필터용 해석 프로그램을 제작하였으며, 그 프로그램에 의한 시뮬레이션 결과를 실제 제작된 시작품의 성능과 비교해 봄으로써 타당성을 검증하였다. 이 해석 프로그램을 바탕으로 설계변수의 조정에 따른 성능변수의 변화 경향을 분석함으로써 최적 설계 알고리즘을 개발하였으며. 그 타당성 및 효용성을 기 상용화된 제품들에 대해 시험 설계해 봄으로써 증명하였다.

• 한국군사과학기술학회지
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• 제4권2호
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• pp.122-129
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• 2001

A characterization procedure for analyzing symmetric coupled MIS(Metal-Insulator-Semiconductor) transmission line is used the same procedure as a general single layer symmetric coupled line with perfect dielectric substrate from the extraction of the characteristic impedance and propagation constant for even- and odd-mode. In this paper, an analysis for a new substrate shielding symmetric coupled MIS structure consisting of grounded crossbar at the interface between Si and SiO2 layer using the Finite- Difference Time-Domain(FDTD) method is presented. In order to reduce the substrate effects on the transmission line characteristics, a shielding structure consisting of grounded crossbar lines over time-domain signal has been examined. Symmetric coupled MIS transmission line parameters for even- and odd-mode are investigated as the functions of frequency, and the extracted distributed frequency- dependent transmission line parameters and corresponding equivalent circuit parameters as well as quality factor for the new MIS crossbar embedded structure are also presented. It is shown that the quality factor of the symmetric coupled transmission line can be improved without significant change in the characteristic impedance and effective dielectric constant.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
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• pp.252-257
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• 1988

This paper discribes an improved technique for locating partial discharge sites within operating transformers by ultrasonic method which utilizes the different travel times of the electrical and ultrasonic signals produced by partial discharges to determine the location of the sources. The technique was to develope the measurement system based on the enhancement of the acoustic emission signals using signal square, circuit to improve the detectable sensitivity and reliability. Also an ultrasonic pulse generator was designed and made to transmit periodically pulses equivalent to pratial discharges and to check the good performance of the system, echo effects and self-diagnosis. Through the laboratory work, it was confirmed that the system and the generator can be used satisfactorily for diagnosing power transformers and for studying echo effects and self-diagnosis of the system.

• 전력전자학회논문지
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• 제17권6호
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• pp.546-552
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• 2012

This paper presents an active anti-islanding detection method using negative sequence voltage injection to the grid through a three-phase photovoltaic inverters. Because islanding operation mode can cause a variety of problems, the islanding detection of grid-connected photovoltaic inverter is the mandatory feature. The islanding mode is detected by measuring the magnitude of negative sequence impedance calculated by the negative sequence voltage and current at the point of common coupling. Simulation and experimental test are performed to verify the effectiveness of the proposed method which can detect the islanding mode in the specified time. The test has been done in accordance with the condition on IEEE Std 929-2000.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.193-196
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• 2000

A new type low-pass filter design method based on a coupled line and transmission line theory is proposed to suppress harmonics by attenuation poles in the stop band. The design formula are derived using the equivalent circuit of a coupled transmission line. The new low-pass filter structure is shown to have attractive properties such as compact size, wide stop band range and low insertion loss. The seventh-order low-pass filter designed by present method has a cutoff frequency of 0.9 CHz with a 0.01 dB ripple level. The coupled line type low-pass filter with strip line configuration was fabricated by using a high-temperature superconducting (HTS : YBa$_2$Cu$_3$O$_{7-{\delta}}$ thin film on MgO(100) substrate. Since the HTS coupled tine type low-pass filter was proposed with five attenuation poles in stop band such as 1.8, 2.5, 4, 5.5, 6.2 GHz. The fabricated low-pass filter has improved the attenuation characteristics up to seven times of the cutoff frequency.

• 대한전자공학회논문지TC
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• 제49권2호
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• pp.39-49
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• 2012

병렬 스터브를 이용하여 개구면 결합 마이크로스트립 패치 안테나 (ACMPA)의 임피던스 대역폭을 넓히는 방법에 대해 연구하였다. H-모양의 개구면을 가지는 일반적인 ACMPA를 설계하고 등가회로의 전기적 파라미터를 추출하였다. 급전선로에 병렬 스터브를 삽입하여 ACMPA의 임피던스 대역폭을 확장시키는 방법을 제시하였다. 병렬 스터브를 삽입한 ACMPA의 -10dB 임피던스 대역폭은 최대 약 14 %로 일반적인 ACMPA의 최대 임피던스 대역폭 5.4 %와 비교하여 대역폭이 약 160 % 증가함을 볼 수 있었다.

• 한국항행학회논문지
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• 제15권4호
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• pp.578-584
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• 2011

본 논문은 집중소자를 사용한 이중대역 비대칭 전력 분배기를 제안 하였다. 분배기는 기존의 비대칭 윌킨슨 전력 분배기를 집중소자를 이용하여 단일대역에서 설계한 후, 여파기 변환 기법을 이용하여 이중대역 특성을 갖도록 설계하였다. 이러한 설계 방법의 특징은 비대칭 분배기 설계 시 마이크로스트립으로 구현이 어려운 높은 임피던스의 전송선로를 집중소자를 이용하여 쉽게 구현할 수 있고, 크기를 작게 할 수 있다는 것이다. 여파기 변환기법에 의한 이중대역 특성을 확인하기 위하여 전력 분배기를 880 MHz와 1650 MHz에서 동작하도록 제작하였으며, 전기적인 특성은 시뮬레이션 결과와 동일하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 연구회
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• pp.25-28
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• 2001

The objectives of this paper are to demonstrate the electrical degradation phenomena with Si atom's behaviors in the grainboundary of semiconducting ZnO ceramics. The ZnO ceramic devices used in this investigation were fabricated by standard ceramic techniques. Especially, $SiO_2$ were added to analyze the degradation characteristics with Si and sintered in oxygen ambient at $1300^{\circ}C$. The conditions of DC degradation test were $115{\pm}2^{\circ}C$ for 13h. Using XRD and SEM, the phase and microstructure of samples were analyzed respectively. E-J analysis was used to determine $\alpha$. Frequency analysis was accomplished to understand $R_g$ and $R_b$ at the equivalent circuit. Electrical stability improved as the amount of $SiO_2$ addition increased. This results were explain by the quantitative analysis and the line scanning method of EPMA.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.637-638
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• 2006

Different from the conventional motor, the superconducting motor has so large air-gap that the actual parameters such as excitation voltage have considerable difference from the values obtained from 2-dimensional electromagnetic analysis. This paper introduces 3-dimensional EMCH(Equivalent Magnetic Circuit Network) method or FLUX-3D FEM(Finite Element Method) software to reduce the error originated from the 2-dimensional electromagnetic analysis for the development of a 1 MW class high-temperature superconducting motor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.1260-1263
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• 2000

Vector control of a single phase induction machine(SPIM) is usually employed by mechanical methods than electrical ones. The disadvantage of a SPIM has large noise at the starting. Using auxiliary winding which is only utilized for starting, the SPIM can be controlled with the vector control method. Regarding a auxiliary winding one phase, the SPIM is analyzed by the unsymmetrical two phase motor and phase transformation is unnecessary such as three phase IM. Including a auxiliary winding, SPIM is modeled by mathematical getting by component of turns ratio with main to auxiliary winding. It will be take with complicated resultant formula, by comparison to symmetrical three phase TM. For using the vector control theory, it must be decoupled of rotor flux and torque component. stator current is controlled and decoupled. This paper presents a variable-speed control system of SPIM, which to decoupled with flux and torque component and to use machine equivalent circuit referred to rotor, conventionally three phase IM by similar method.