• 한국전기전자재료학회논문지
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• 제25권2호
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• pp.147-152
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• 2012

This paper dealt with the frequency component analysis of acoustic signals produced by corona and series-arc discharges as a diagnostic technique for closed-switchboards. Corona and series-arc discharge were simulated by a needle-plane electrode and an arc generator specified in UL1699, respectively. Acoustic signal was detected by a wideband acoustic sensor with a frequency bandwidth of 4 Hz~100 kHz (-3 dB). We analyzed frequency spectrums of the acoustic signals detected in various discharge conditions. The results showed that acoustic signals mainly exist in ranges from 30 kHz to 60 kHz. From the experimental results, an acoustic detection system which consists of a constant current power supply (CCP), a low noise amplifier (LNA) and a band pass filter was designed and fabricated. The CCP separates the signal component from the DC source of acoustic sensor, and the LNA has a gain of 40 dB in ranges of 280 Hz~320 kHz. The high and the low cut-off frequency are 30 kHz and 60 kHz, respectively. We could detect corona and series-arc discharges without any interference by the acoustic detection system, and the best frequency is considered in ranges of 30 kHz~60 kHz.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.2070-2078
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• 2014

In this work, the frequency response of gate-all-around (GAA) Ge/GaAs heterojunction tunneling field-effect transistor (TFET) with hetero-gate-dielectric (HGD) and pnpn channel doping profile has been analysed by technology computer-aided design (TCAD) device-circuit mixed-mode simulations, with comparison studies among ppn, pnpn, and HGD pnpn TFET devices. By recursive tracing of voltage transfer curves (VTCs) of a common-source (CS) amplifier based on the HGD pnpn TFET, the operation point (Q-point) was obtained at $V_{DS}=1V$, where the maximum available output swing was acquired without waveform distortion. The slope of VTC of the amplifier was 9.21 V/V (19.4 dB), which mainly resulted from the ponderable direct-current (DC) characteristics of HGD pnpn TFET. Along with the DC performances, frequency response with a small-signal voltage of 10 mV has been closely investigated in terms of voltage gain ($A_v$), unit-gain frequency ($f_{unity}$), and cut-off frequency ($f_T$). The Ge/GaAs HGD pnpn TFET demonstrated $A_v=19.4dB$, $f_{unity}=10THz$, $f_T=0.487$ THz and $f_{max}=18THz$.

• 전자공학회논문지C
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• 제35C권6호
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• pp.30-38
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• 1998

본 논문에서는 능동필터 설계시 기본 블록으로 이용될 수 있으며, 저전압 고주파에서 동작 가능한 새로운 구조의 CMOS 전류모드 적분기를 제안하였다. 더불어 전압조절을 통해 그 이득과 주파수를 제어할 수 있는 트랜스컨덕턴스 제어회로를 설계하였다. 제안된 적분기는 CMOS 상보형 회로로 구성하였으며, 따라서 적분기의 단위이득주파수에 영향을 주는 적분기의 트랜스컨덕턴스를 증가 시켰다. 제안된 적분기의 단위이득 주파수는 NMOS-gm을 가지는 기존의 적분기에 비하여 두 배 가까이 증가되었다. 또한 트랜스컨덕턴스 제어회로를 이용하여 능동필터의 공정시 나타날 수 있는 오차를 줄이고, 그 용도에 따라 주파수와 이득제어를 가능하게 하였다. 이의 응용회로로서 3차 체비셰프 저역필터를 0.8㎛ CMOS 파라메터를 이용하여 설계하였으며, 이러한 결과들은 소신호 해석 및 0.8㎛ 공정 파라미터를 갖는 HSPICE 시뮬레이션을 통하여 검증되었다.

• Journal of electromagnetic engineering and science
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• 제14권1호
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• pp.36-42
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• 2014

In this paper, an epsilon near zero (ENZ) tunneling circuit using a double-ridge rectangular waveguide (RWG) is proposed for the miniaturization of a waveguide component. The proposed ENZ channel and is located in the middle of the input-output RWG (IORWG). The ratio of the height to the width of the channel waveguide is very small compared to the IORWG. By properly adjusting the ridge dimensions, the tunneling frequency of the proposed ENZ channel can be lowered to near the cut-off frequency of the IORWG. For the proposed ENZ tunneling circuit, the approach adopted for extracting the effective permittivity, effective permeability;normalized effective wave impedance, and propagation constant from the simulated scattering parameters was explained. The extracted parameters verified that the proposed channel is an ENZ channel and electromagnetic energy is tunneling through the channel. Simulation and measurement results of the fabricated ENZ channel structure agreed.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1763-1768
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• 2016

This paper presents the electrical characteristics of the gallium nitride (GaN) current aperture vertical electron transistor (CAVET) by using two-dimensional (2-D) technology computer-aided design (TCAD) simulations. The CAVETs are considered as the alternative device due to their high breakdown voltage and high integration density in the high-power applications. The optimized design for the CAVET focused on the electrical performances according to the different gate-source length ($L_{GS}$) and aperture length ($L_{AP}$). We analyze DC and RF parameters inducing on-state current ($I_{on}$), threshold voltage ($V_t$), breakdown voltage ($V_B$), transconductance ($g_m$), gate capacitance ($C_{gg}$), cut-off frequency ($f_T$), and maximum oscillation frequency ($f_{max}$).

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.301-303
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• 2001

In this paper we present a Capacitor Charging Power Supply (CCPS) using a series-resonant three-level inverter topology to improve voltage regulation and use semiconductor switches having low blocking voltage capability such as MOSFETs. This inverter can be operated with two modes, Full Power Mode (FPM) and Half Power Mode (HPM). In FPM inverter supplies the high frequency step up transformer with full DC-link voltage and in HPM with half DC-link voltage. HPM switching method will be adopted when CCPS output voltage reaches the preset target value and operates in refresh mode-charge is maintained on the capacitor. In this topology each semiconductor devices blocks a half of the DC-link voltage[2]. A 15kW, 30kV CCPS has been built and will be tested for an electric precipitator application. The CCPS operates from an input voltage of 500VDC and has a variable output voltage between 10 to 30kV and 1kHz repetition rate at 44nF capacitive load [3]. A resonant frequency of 67.9kHz was selected and a voltage regulation of $0.83\%$ has been achieved through the use of half power mode without using the forced cut off the switch current [1]. The theory of operation, circuit topology and test results are given.

• 한국정밀공학회지
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• 제26권2호
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• pp.35-44
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• 2009

Long stroke Fast Tool Servo (LFTS) with maximum stroke of $432{\mu}m$ is designed, manufactured and tested for fabrication of optical free-form surfaces. The large amount of stroke in LFTS has been realized by utilizing the hinge and lever mechanisms which enable the displacement amplification ratio of 4.3. In this mechanism the peculiar shape was devised for maximizing the displacement of end tip in LFTS and special mechanical spring has been mounted to provide the sufficient preload to the piezoelectric actuator. Also, its longitudinal motion of tool tip can be measured by capacitive type displacement sensor and closed-loop controlled to overcome the nonlinear hysteresis. In order to verify the static and dynamic characteristics of designed LFTS, several features including step response, frequency response and cut-off frequency in closed-loop mode were experimentally examined. Also, basic machining result shows that the proposed LFTS is capable of generating the optical free-form surface as an additional axis in diamond turning machine.

• 한국전기전자재료학회논문지
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• 제19권4호
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• pp.339-343
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• 2006

We observed the application possibility of inductive coupler for the underground high-voltage power line communication by means of analysis of signal transmission characteristics and magnetic properties on annealing temperatures for high-permeability Fe-base amorphous alloys. The best electromagnetic and transmission characteristics were shown in nano-crystalline precipitated alloy annealed at temperature $510^{\circ}C$. The transmission characteristics in the low-frequency band depend on permeability of magnetic core materials and its properties of high-frequency band can be improved by impedance matching. Using the high pass filter embedded in the coupler, other noise signal band except for communication signals could be cut off.

• 한국컴퓨터정보학회논문지
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• 제3권2호
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• pp.77-84
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• 1998

요즈음 CMOS 기술의 발전에 의해서 연속시간 신호시스템이 매우 각광을 받고 있다. 따라서 이 논문에서는 음성신호 처리영역에서 동작하는 CMOS floating 저항을 이용한저역통과 필터를 설계하였다. 특히 이 논문에서는 포화영역에서 동작하는 all CMOS floating 저항을 설계하였으며, $\pm$1V 영역에서 $\pm$0.04%의 선형성이 얻어졌다. 주파수 응답은10MHz를 초과하였으며 능동 RC회로의 집적화에 매우 유용할것으로 생각한다. 이 방법에 의해 설계도니 저역통과필터는 SC 필터보다 그 구조가 간단하므로 IC의 형태로 만들 때 칩 면적을 많이 줄일 수 있다. 설계된 필터의 특성은 pspice에 의해 시뮬레이션 하였으며, 그 특성이 우수함이 입증되었다.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권1호
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• pp.32-38
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• 2002

This paper describes a development of a portable physical activity monitoring system using two accelerometers to quantify physical activity. The system hardware consists of two piezoresistive accelerometers, amplifiers with gain of 30, lowpass filters with cut-off frequency of 15Hz, offset control circuits, one-chip microcontroller and flash memory card. In order to evaluate the performance of the system we acquired 3 channel data at 32 sample/sec from body-fixed accelerometers in chest and right upper leg. And then the acquired data were processed by MatLab on personal computer. We tried to distinguish not only fundamental actions which are steady-state activities such as standing, sitting, and lying but also dynamic activities with walking, up a stairway, down a stairway, and running. Five subjects participated the evaluation process which compare the video data with the measured data. As a result, the activity classification rate of 90.6% on average was obtained. Overall results showed that the steady-state activities could be classified from the low component of 3-axis acceleration signal and dynamic activities could be distinguished from frequency analysis using wavelet transform and FFT. Finally, we could find that this system can be applied to acquire and analyze the static and dynamic physical activity data.