• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.418-421
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• 2001

The ceramic filters were developed using technology similar to that of quartz crystal and electromechanical filter. However, the key to this development involved the theoretical analysis of vibration modes and material improvements of piezoelectric ceramics. The primary application of ceramic filters has been for consumer-market use. Accordingly, a major emhpasis has involved mass production technology, leading to low-priced devices. A typical ceramic filter includes monolithic resonators and capacitors packaged in unique configurations. Nakazawa developed a double-mode resonator as two acoustically coupled single resonators. And he developed 10.7MHz crystal filters using multi-energy trapping mode of thickness shear vibration. He succeeded in realizing a two-pole band pass filter response without external inductance by splitting a dot electrode to creat coupled symmetric and antisymmetric vibration modes. Accordingly, the simulation for ceramic filter were important. So that, this paper were investigated the pass frequency of filter on the electrode length and thickness of ceramic.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.553-555
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• 1996

This paper concerns with a method to improve the current and power waveforms of the variable speed $3{\Phi}$ AC motor system driven by the single-pulse PWM, and the current waveforms and $3{\Phi}$ power waveforms are analyzed by FFT under various running conditions. By the performance analysis through the experiments, the following results have been obtained. AC source of pseudo sine waveform can be obtained from the modulated alternating square voltage by means of the well designed LC filter. It is confirmed that current waveforms and $3{\Phi}$ power waveforms can be improved by utilizing the high order low pass LC filter than that of lower order. Especially, current waveforms and $3{\Phi}$ power waveforms tan be much improved at low frequency domain. $3{\Phi}$ power waveforms have a smatter ripple and bigger power by utilizing the high order low pass LC filter than that of lower order. Also, the running condition of $3{\Phi}$ AC motor is good at low frequency domain.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1447-1453
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• 2014

This paper proposes the new method based on the availability of three points measurement and convexity of photovoltaic (PV) curve characteristic at the maximum power point (MPP). In general, the MPP tracking (MPPT) function is the important part of all PV systems due to their power-voltage (P-V) characteristics related with weather conditions. Then, the analog-to-digital converter (ADC) and low pass filter (LPF) are required to measure the voltage and current for MPPT by the digital controller, which is used to implement the PV power conditioning system (PCS). The measurement and quantization error due to rounding or truncation in ADC and the delay of LPF might degrade the reliability of MPPT. To overcome this limitation, the proposed method is proposed while improving the performances in both steady-state and dynamic responses based on the detailed investigation of its properties for availability and convexity. The performances of proposed method are evaluated with the several case studies by the PSCAD/EMTDC$^{(R)}$ simulation. Then, the experimental results are given to verify its feasibility in real-time.

• ETRI Journal
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• 제29권2호
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• pp.212-218
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• 2007

A novel low-voltage CMOS current feedback operational amplifier (CFOA) is presented. This realization nearly allows rail-to-rail input/output operations. Also, it provides high driving current capabilities. The CFOA operates at supply voltages of ${\pm}0.75V$ with a total standby current of 304 ${\mu}A$. The circuit exhibits a bandwidth better than 120 MHz and a current drive capability of ${\pm}1$ mA. An application of the CFOA to realize a new all-pass filter is given. PSpice simulation results using 0.25 ${\mu}m$ CMOS technology parameters for the proposed CFOA and its application are given.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.316-320
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• 2008

This paper described the design and fabrication of a series arc detection module to monitor electrical insulation in low-voltage system. The module consists of a passive high-pass filter with a low cut-off frequency of 3 kHz to attenuate power frequency voltage by 80 dB and an active band-pass filter with a frequency of 4 kHz to detect series arc signals only. For the application experiment, we simulated series arcing phenomena on various loads such as incandescent lamp controlled by dimmer and inverter fed induction motors by an arc generator specified in UL1699. From the experimental results, we could detect series arc signals without an influence of noises.

• 한국전자파학회논문지
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• 제21권3호
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• pp.307-314
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• 2010

본 논문에서는 새로운 초광대역 마이크로스트립 선로-suspended 스트립 선로(SSL) 전이 구조를 제안하였고, 이 전이 구조를 이용하여 저손실의 높은 선택도를 갖는 여파기를 구현할 수 있음을 보여주었다. 제안된 전이구조는 광대역의 특성을 가지고 있으므로, SSL 여파기의 설계를 간단하게 할 수 있게 하고, 구현 시 별도의 튜닝이 필요 없음을 보여주었다. SSL 여파기 구현의 예로서 SSL 저역 및 고역 통과 여파기를 각각 구현하고, 이를 연결함으로써 2.3~10.5 GHz 대역에서 1.2 dB 이하의 적은 삽입 손실을 가지고, 또한 고선택도를 가지는 대역 통과 여파기를 구현한 것을 보여주고 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.103-105
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• 2004

In this paper, a novel control scheme compensating for source voltage unbalance and current harmonics and power factor simultaneously in unified active power filter systems combined with shunt passive filters is proposed, where no low/high-pass filter are used in deriving the reference voltage for compensation. Using digital all-pass filters, the phase angle and the reference voltages compensating for harmonic current and unbalanced voltage are derived from the positive sequence component of the unbalanced voltage. The amplitude of d-axis current in a series filter is controlled as zero for power factor correction. The validity of the proposed control scheme has been verified by experimental results.

• 전기학회논문지
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• 제60권4호
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• pp.871-876
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• 2011

In this paper, a voltage-controlled frequency tunable current-mode integrator and a 3rd-order current-mode Chebyshev filter in 1.8V-$0.18{\mu}m$ CMOS is realized for software radio applications in system-on-chips. This filter is used for reconstruction purposes between a current-steering DAC and a current-mode mixer. Power consumption of the designed filter can be reduced by using a current-mode small size integrator. And also, cutoff frequency of this filter is variable between 1.2MHz and 10.1MHz, the power consumption is 2.85mW. And the voltage bias compensated circuit is used to control the voltage variation.in the designed filter.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.405-408
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• 2001

This paper investigates the problem of the speed estimation of conventional speed sensorless stator flux-oriented induction machine drive in the field weakening region and proposes a new speed estimation scheme to estimate speed exactly in transients in the field weakening region. The error included in the estimated rotor speed is removed by not a low pass filter but Kalman filter.

• 한국전기전자재료학회논문지
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• 제18권8호
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• pp.739-746
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• 2005

When we design a binary phase holographic optical low-pass filter (HOLF), the phase difference is generally set to be $\pi$ to optimize the diffraction efficiency. However, the phase difference of real HOLF mostly deviate from $\pi$ by the error in the fabrication process. The deviation causes the (0,0)-th order diffracted beam to increase, which results In raising the diffraction efficiency. To study the effects of the phase error on the performance of HOLF, we calculated the MTF of HOLF for various phase differences. The results show that the phase error of 10 $\%$ makes little change in the filtering characteristics of HOLF. Considering the filtering by lens and CCD, the effects of the phase error becomes much smaller. To confirm it experimentally, we fabricated HOLFs for various phase differences. After installing it in a digital camera, we take picture of test targets and observe the Moire fringes and the resolution. The results agree with our prediction.