• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.150-150
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• 2011

Electron-neutral collision frequency is one of the important parameters in the plasma physics. Recently, It is employed to monitor the plasma processing in industrial plasma engineering [1]. Using the wave-cutoff probe with network analyzer, the plasma impedance was measured in inductively coupled argon plasma and analyzed to determine the resonance frequency. The electron-neutral collision frequency is directly calculated from the resonance frequency. The calculated electron-neutral collision frequency is good agree with reference which is calculated by measured EEDF using single langmuir probe (SLP).

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.467-472
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• 2007

A modern MEMS resonator is a micro-scale structure operated over a high frequency range. In order to predict its resonant behavior in a design process, High-frequency response analysis (Hi-FRA) is demanded. Algebraic substructuring (AS) is known as a fast numerical technique to construct an eigenspace for FR and frequency sweep (FS) algorithm efficiently solves the frequency response system projected on the eigenspace. However, the existing FS algorithm using AS is developed for low-FRA, say over the range 1Hz-2KHz. In this work, we extend the FS algorithm using AS for FRA over an arbitrary frequency range. Therefore, it can be efficiently applied to systems operated at a high frequency, say over the range 230MHz-250MHz. The success of the proposed method is demonstrated by Hi-FRA of a checkerboard resonator.

• 한국군사과학기술학회지
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• 제14권3호
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• pp.372-379
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• 2011

Estimating underwater target state variables(position, velocity, course, etc) is necessary to counteract threatening targets. In passive sonar systems, conventional target motion analysis(TMA) techniques using bearing and frequency measurements of an underwater target are widely introduced. However, it is not clear how conventional TMA techniques can be used if some of frequency measurements are unavailable during parts of the scenario, partially unavailable frequency measurements are common in the ocean with complicated acoustic conditions where frequency measurements often come and go. This paper proposes a new TMA algorithm, which is robust to partially unavailable frequency measurements, using the frequency measurements fusion method.

• 전력전자학회논문지
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• 제21권2호
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• pp.168-174
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• 2016

In this paper, current control using PI controller in the synchronous reference frame is analyzed through the relationship among bandwidth, resonance frequency, and sampling frequency in the grid-connected inverter with LCL filter. Stability is investigated by using bode plot in frequency domain and root locus in discrete domain. The feedback variable is the grid current, which is regulated by the PI controller in the synchronous reference frame. System delay is modeled as 1.5Ts, which contains computational and PWM modulator delay. Two resonance frequencies are given at 815 Hz and 3.16 kHz from LCL filter parameters. Sufficient phase and gain margins can be obtained to guarantee stable current control, in case that resonance frequency is above one-sixth of the sampling frequency. Unstable current control is performed when resonance frequency is below one-sixth of the sampling frequency. Analysis results of stability from frequency response and discrete response is the same regardless of resonance frequency. Finally, stability of current control based on theoretical analysis is clearly verified through simulation and experiment in grid-connected inverters with LCL filter.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.1127-1130
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• 1999

In this paper, using one method of Additive Synthesis, Analysis-by-synthesis/Overlap-Add (ABS/OLA) method, analysis and synthesis of musical tones is processed. But peak detection of frequency domain is processed by proposed method considering the view of acoustics. It is that that harmonics frequency is times of main frequency. Using this fact, peak detection of frequency domain is useful for detection of tonal component identified musical note. It is possible to realize high-quality lour bit rate audio.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.45-48
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• 1999

The demands of WLAN(Wireless Local Area Network) systems increase rapidly in whole society and this phenonenon has been expected that WLAN wi11 substitute for wired-LAN. The FHSS(Frequency Hopped Spread Spectrum) method using the WLAN is changed to the performance of Frequency synthesizer. In this paper, we proposed pipeline-accumulator using ring-counter method instead of constant accumulator that has demerits of size and power consumption. Designed DDFS generated operating frequency of 167MHz and maximum output frequency of 83.5MHz.

• 전기학회논문지P
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• 제59권3호
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• pp.253-257
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• 2010

The frequency is an important operation parameter for the control, protection, and stability of a power system. The frequency as a key index of power quality can be indicative of system abnormal conditions and disturbances. Due to the sudden change in generation and loads or faults in power system, the frequency is supposed to deviate from its nominal value. It is essential that the frequency must be maintained very close to its nominal frequency. An accurate monitoring of the power frequency is essential to optimal operation and prevention for wide area blackout. As most conventional frequency estimation schemes are based on DFT filter, it has been pointed out that the gain error could cause defects when the frequency is deviated from nominal value. This paper presents an advanced frequency estimation technique using gain compensation to improve the performance of DFT filter based techniques. To evaluate performance of the proposed algorithm, the 765kV T/L system in Korea is simulated by EMTP-RV software. The proposed technique can reduce the gain error caused when the power system frequency deviates from nominal value.

• 전기학회논문지
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• 제60권8호
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• pp.1492-1501
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• 2011

A wide-area protection intelligent technique has been used to improve a reliability in power systems and to prevent a blackout. Nowadays, voltage and current phasor estimation has been executed by GPS-based synchronized PMU, which has become an important way of wide-area blackout protection for the prevention of expending faults in power systems. As this technique has the difficulties in collecting and sharing of information, there have been used a FNET method for the wide-area intelligent protection. This technique is very useful for the prediction of the inception fault and for the prevention of fault propagation with accurate monitoring frequency and frequency deviation. It consists of FDRs and IMS. It is well known that FNET can detect the dynamic behavior of system and obtain the real-time frequency information. Therefore, FDRs must adopt a optimal frequency estimation method that is robust to noise and fault. In this paper, we present comparative studies for the frequency estimation method using IRDWT(improved recursive discrete wavelet transform), for the frequency estimation method using FRDWT(fast recursive discrete wavelet transform). we used the Republic of Korea 345kV power system modeling data by EMTP-RV. The user-defined arbitrary waveforms were used in order to evaluate the performance of the proposed two kinds of RDWT. Also, the frequency variation data in various range, both large range and small range, were used for simulation. The simulation results showed that the proposed frequency estimation technique using FRDWT can be the optimal frequency measurement method applied to FDRs.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.223-226
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• 1999

We study the propagation property of the transient signals along the microstrip using the wavelet transform. Wavelet transform can offer the time-frequency windows. It makes the resolution of time high in high frequency range and the resolution of frequency high in low frequency range. So It is useful to analyze the signals which have both low and high frequency components.

• 한국통신학회논문지
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• 제36권2A호
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• pp.127-132
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• 2011

본 논문은 Chirp 신호가 변조된 UWB frequency slope를 이용한 거리 측정 기술 및 통신 시스템을 제안하였다. 오직 up-chirp 만 사용하거나 혹은 (주파수 간) 동일한 주파수 변화도(frequency sweeping rate)를 가진 down-chirp 만 사용하는 대신에, 제안된 시스템은 주파수 도약을 이용하여 서로 다른 주파수 변화도를 가지는 여러 Chirp 신호를 사용한다. 제안된 시스템은 데이터 전송 속도를 증가시킬 수 있고 동시에 사용자들이 사용한 sequence 간에 간섭도 줄일 수 있기 때문에 기존 통신 거리 측정 전략보다도 성능이 좋다. 본 논문에서는 연구의 타당성을 보이기 위해 MATLAB을 이용한 UWB 통신 시스템의 시뮬레이션을 제시한다.