• 한국정밀공학회지
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• 제16권5호통권98호
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• pp.19-28
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• 1999

In this study, a real-time simulation system and a washout algorithm for an excavator have been developed for a driving simulator with six degrees of freedom. The excavator model consisting of a boom. bucket, upper frame, lower frame and four wheels, has total 11 degrees of freedom. The suggested washout algorithm consists of high and low pass filters with second order. The high pass filters cut off low frequency of the motion cues limited by platform motion. The cut off frequency for the tilt coordination are suggested for a realistic regeneration of excavator motion.

• 전기전자학회논문지
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• 제16권2호
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• pp.116-120
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• 2012

본 논문에서는 밀리미터파 응용에 사용 가능한 우수한 성능의 50 nm InGaAs/InAlAs/GaAs metamorphic HEMT를 구현하였다. 게이트 길이가 50 nm이며 단위 게이트 폭이 30 ${\mu}m$인 2개의 게이트를 가지고 있는 MHEMT의 측정결과, 740 mA/mm의 드레인 포화 전류밀도와 1.02 S/mm의 상호전달 전도도를 얻었으며 전류이득차단주파수와 최대공진주파수는 각각 430 GHz와 406 GHz의 특성을 나타내었다.

• 전기학회논문지
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• 제66권6호
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• pp.898-904
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• 2017

DFT(Discrete Fourier Transform) is one of the most widely used method to estimate the phasor of a relaying signal. The harmonics are eliminated by the DFT. However, high frequency components, except for harmonics, are not removed and cause an error in DFT-based phasor estimation process. This paper suggests high frequency noise reduction method by using a newly designed low-pass filter to estimate a signal phasor. When selecting a stop-band cut-off frequency of the low-pass filter, high frequency components generated by faults are considered. To reduce the phasor estimation delay caused by a low-pass filter, this paper proposes a low-pass filter whose settling time is reduced. An adverse effect of high frequency noise on DFT-based phasor estimation is reduced. To evaluate the performance of the proposed method, signals which are collected under a fault condition at a 345[kV] transmission system modeled by EMTP-RV are used.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1345-1347
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• 2008

This paper described a method of determining whether arcing is present in a low-voltage wiring system. We simulated the series arcing that generated in electrical loads and fabricated a arc detection module which can discriminate between normal and arcing state. The module consists of a high-pass filter with a low cut-off frequency of 3 kHz to attenuate power frequency voltage and an active band-pass filter with a frequency of 4 kHz ${\sim}$ 8 kHz to detect series arc signals only. We tested an Incandescent lamp that was controlled by a dimmer and analysed. The module consists of a 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. From the experimental results, we could detect series arc signals without an influence of non-linear loads.

• ETRI Journal
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• 제27권3호
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• pp.304-311
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• 2005

We report on the fabrication of an AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (PHEMT) using a dielectric-defined process. This process was utilized to fabricate $0.12\;{\mu}m\;{\times}\;100 {\mu}m$ T-gate PHEMTs. A two-step etch process was performed to define the gate footprint in the $SiN_x$. The $SiN_x$ was etched either by dry etching alone or using a combination of wet and dry etching. The gate recessing was done in three steps: a wet etching for removal of the damaged surface layer, a dry etching for the narrow recess, and wet etching. A structure for the top of the T-gate consisting of a wide head part and a narrow lower layer part has been employed, taking advantage of the large cross-sectional area of the gate and its mechanically stable structure. From s-parameter data of up to 50 GHz, an extrapolated cut-off frequency of as high as 104 GHz was obtained. When comparing sample C (combination of wet and dry etching for the $SiN_x$) with sample A (dry etching for the $SiN_x$), we observed an 62.5% increase of the cut-off frequency. This is believed to be due to considerable decreases of the gate-source and gate-drain capacitances. This improvement in RF performance can be understood in terms of the decrease in parasitic capacitances, which is due to the use of the dielectric and the gate recess etching method.

• 한국전자통신학회논문지
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• 제19권1호
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• pp.19-24
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• 2024

본 논문에서는 기존의 접힌 도파관의 내부 구조물을 Y형으로 대체하여 도파관의 차단주파수를 낮춘 접힌 Ridge 도파관(FRWG)을 제안하였다. 제안된 FRWG는 역 Ridge 도파관으로 등가될 수 있는데, 측면의 높이를 줄였을 때 측면의 길이가 증가하여 동일한 크기의 도파관에 비해 차단주파수를 절반 이하로 줄일 수 있다. 논문에서는 길이 40mm, 높이 20mm의 도파관에 폭 2mm의 Y형 구조물을 넣어 1.996GHz의 차단주파수를 갖는 FRWG를 설계하였다. 또한, 제안된 도파관을 활용하기 위한 SMA 커넥터와의 트랜지션이 설계되었다. 트랜지션은 커넥터의 신호선과의 커패시턴스를 최적화하여 2.064 ~ 3.050GHz 대역에서 VSWR 2:1 이하의 특성을 나타내었다. 제안된 FRWG는 도파관 구조를 이용한 다양한 소자의 소형화에 응용할 수 있다.

• 한국항행학회논문지
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• 제25권5호
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• pp.363-369
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• 2021

본 논문에서는 텔레메트리 시스템을 위한 가변 컷 오프 주파수 및 가변 샘플레이트 특성을 지니는 저면적 다채널 디지털 필터구조를 제안한다. 제안하는 디지털 필터는 임의의 컷 비율에 대해 필터 뱅크의 추가적인 설계 없이 컷 오프 주파수와 샘플레이트를 가변적으로 사용할 수 있는 필터 뱅크를 구현함으로써 하드웨어 면적을 줄일 수 있었다. 또한, 멀티플렉서 (MUX; Multiplexer) 컨트롤을 통해 통과하는 필터의 개수에 따라 샘플레이트를 가변적으로 선택할 수 있는 구조를 제안한다. 제안하는 디지털 필터는 Quartus의 FIR (finite impulse response) IP (intellectual property)의 TDM (time division multiplexing)을 이용함으로써, TDM을 사용하지 않았을 때보다 면적이 큰 DSP (digital signal processing) 블록을 80개에서 1개로 줄일 수 있었다. Kaiser 창 함수를 이용하여 Matlab을 통해 필터의 차수와 계수를 계산하였으며, VHDL (very high speed integrated circuits hardware description language)을 통해 하드웨어로 구현하였다. 텔레메트리 시스템에 적용 후, 실험 결과를 통해 제안하는 디지털 필터가 정상적으로 동작하고 있음을 확인하였다.

• 한국유체기계학회 논문집
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• 제2권3호
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• pp.45-51
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• 1999

Centrifugal fans are widely used and the noise generated by these machines causes one of the most serious problems. In general, the centrifugal fan noise is often dominated by tones at BPF(blade passage frequency) and its higher harmonics. This is a consequence of the strong interaction between the flow discharged from the impeller and the cutoff in the casing. However, only a few researches have been carried out on predicting the noise due to the difficulty in obtaining detailed information about the flow field and casing effects on noise radiation. The objective of this study is to develop a prediction method for the unsteady flow field and the acoustic pressure field of a centrifugal fan and to calculate the effects of rotating velocity, flow rate, cut-off distance and the number of blades and its effects on the noise of the fan. We assume that the impeller rotates with a constant angular velocity and the flow field around the impeller is incompressible and inviscid. So, a discrete vortex method (DVM) is used to model the centrifugal fan and to calculate the flow field. The force of each element on the blade is calculated with the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. The cut-off distance is the most important factor effecting the noise generation. Acoustic pressure is proportional to 2.8, which shows the same scaling index as the experimental result. In this paper, the cut-off distance is found to be the dominant parameter offecting the acoustic pressure.

• 전기학회논문지
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• 제65권10호
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• pp.1706-1711
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• 2016

Electromagnetic wave simulation was performed to predict characteristics of manufactured cutoff probe at low temperature magnetized plasma medium. Microwave cutoff probe is designed for research the properties of magnetized inductively coupled plasma. It was shown that the cutoff probe method can safely be used for weakly magnetized high density plasma sources. Cutoff probe system with two port network analyzer has been prepared and applied to measure electron density distributions in large area, 13.56MHz driven weakly magnetized inductively coupled plasma source. The results shown that, the plasma frequency confirmed cut-off characteristics in low temperature plasma. Especially, cut-off characteristics was found at upper hybrid resonance frequency in the environment of the magnetic field. In case of a induced weak magnetic field in inductively coupled plasma, plasma density estimated from the cutoff frequency in the same way at unmagnetized plasma due to nearly same plasma frequency and upper hybrid resonance frequency. The plasma density is increased and uniformity is improved by applying a induced weak magnetic field in inductively coupled plasma.

• JSTS:Journal of Semiconductor Technology and Science
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• 제9권4호
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• pp.266-272
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• 2009

In the present work three dimensional process and device simulations were employed to study the performance variations with RTA. It is observed that with the increase in RTA temperature, the arsenic dopants from the source /drain region diffuse laterally under the spacer region and simultaneously acceptors (Boron) are redistributed from the central axis region of the fin towards the Si/SiO2 interface. As a consequence both drive current and peak cut-off frequency of an n-FinFET are observed to improve with RTA temperatures. Volume inversion and hence the flow of carries through the central axis region of the fin due to reduced scattering was found behind the performance improvements with increasing RTA temperature.