• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.251-252
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• 2006

In this paper, we presented an extension of the broadband DOA estimation method using frequency-domain frequency-invariant beamforming (FDFIB). The technique uses FDFIB instead of conventional frequency invariant beamforming (FIB) methods. And different narrowband DOA estimation methods, MUSIC, ESPRIT, and MPM, are used respectively. A comparison is made to demonstrate that the FDFIB-MPM not only offers a better resolution than the FDFIB-MUSIC, FDFIB-ESPRIT, but also it is computationally very efficient.

• 전기학회논문지P
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• 제63권4호
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• pp.241-247
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• 2014

This paper propose a variable parameter estimations of five-phase squirrel-cage induction motor(IM) for speed control system. In order to high performance control of AC motor using a field oriented control(FOC) and direct torque control(DTC) algorithm, there are required precise motor parameters for slip calculation, flux observer, controller gain, rotor position, speed estimation, and so on. We are suggest a analyzed estimation results of the motor parameters that developing five-phase squirrel-cage IM have a stator of concentrated winding for experimental of variable input power frequency. There are results of stator winding test, no-load test, locked-rotor test, variable actual load test, and estimated parameters of equivalent circuits using manufactured experimental apparatus by IEEE Standard Test Procedure for Polyphase Induction Motors and Generators 112-2004.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.125-126
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• 2007

In this paper, we analyze the channel estimation performances associated with the interpolation order for OFDM systems. We first analyze the time varying channel and frequency selective channel, and then we derive the channel Index which indicates the ratio of time axis variation and frequency axis variation. The analyzed results show that time interpolation followed by a frequency interpolation is adequate for the channel with a channel index larger than a certain threshold value and vice versa. Computer simulation explains that the method which decides Interpolation order outperforms fixed order estimation.

• 대한원격탐사학회지
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• 제23권5호
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• pp.421-430
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• 2007

This paper presents the results of the ocean surface current velocity estimation using 6 Radarsat-1 SAR images acquired in west coastal area near Incheon. We extracted the surface velocity from SAR images based on the Doppler shift approach in which the azimuth frequency shift is related to the motion of surface target in the radar direction. The Doppler shift was measured by the difference between the Doppler centroid estimated in the range-compressed, azimuth-frequency domain and the nominal Doppler centroid used during the SAR focusing process. The extracted SAR current velocities were statistically compared with the current velocities from the high frequency(HF) radar in terms of averages, standard deviations, and root mean square errors. The problem of the unreliable nominal Doppler centroid for the estimation of the SAR current velocity was corrected by subtracting the difference of averages between SAR and HF-radar current velocities from the SAR current velocity. The corrected SAR current velocity inherits the average of HF-radar data while maintaining high-resolution nature of the original SAR data.

• ETRI Journal
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• 제41권5호
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• pp.658-669
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• 2019

For dual-channel time-frequency (TF) overlapped signals with low sparsity in underdetermined blind source separation (UBSS), this paper proposes an effective method based on interval probability to estimate and expand the types of mixing matrices. First, the detection of TF single-source points (TF-SSP) is used to improve the TF sparsity of each source. For more distinguishability, as the ratios of the coefficients from different columns of the mixing matrix are close, a local peak-detection mechanism based on interval probability (LPIP) is proposed. LPIP utilizes uniform subintervals to optimize and classify the TF coefficient ratios of the detected TF-SSP effectively in the case of a high level of TF overlap among sources and reduces the TF interference points and redundant signal features greatly to enhance the estimation accuracy. The simulation results show that under both noiseless and noisy cases, the proposed method performs better than the selected mainstream traditional methods, has good robustness, and has low algorithm complexity.

• Ocean and Polar Research
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• 제39권1호
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• pp.13-21
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• 2017

Temporal changes in the number of zooplankton species are important information for understanding basic characteristics and species diversity in marine ecosystems. The aim of the present study was to estimate the optimal monitoring frequency (OMF) to guarantee and predict the minimum number of species occurrences for studies concerning marine ecosystems. The OMF is estimated using the temporal number of zooplankton species through bi-weekly monitoring of zooplankton species data according to operational taxonomic units in the Tongyoung coastal sea. The optimal model comprises two terms, a constant (optimal mean) and a cosine function with a one-year period. The confidence interval (CI) range of the model with monitoring frequency was estimated using a bootstrap method. The CI range was used as a reference to estimate the optimal monitoring frequency. In general, the minimum monitoring frequency (numbers per year) directly depends on the target (acceptable) estimation error. When the acceptable error (range of the CI) increases, the monitoring frequency decreases because the large acceptable error signals a rough estimation. If the acceptable error (unit: number value) of the number of the zooplankton species is set to 3, the minimum monitoring frequency (times per year) is 24. The residual distribution of the model followed a normal distribution. This model can be applied for the estimation of the minimal monitoring frequency that satisfies the target error bounds, as this model provides an estimation of the error of the zooplankton species numbers with monitoring frequencies.

• 한국산학기술학회논문지
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• 제19권11호
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• pp.594-603
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• 2018

최근 계측 기술의 발달에 따라 종래의 복잡하고 시간 소모적인 현장 계측분석 작업을 단순하고 편리하게 만드는 작업이 가능해지고 있다. 이런 배경에서 이 논문에서는 최소화된 계측 및 신호처리를 통해 상시진동 케이블의 장력을 추정하는 문제에 대해 연구하였다. 최소화 계측 방법으로는 저가 영상장비로 촬영된 동영상만을 이용하는 영상 변위 계측을 구상하였다. 또한 이로 인한 유효 주파수 대역 부족 문제의 해결을 위해 미러 주파수를 이용한 고유진동수 추정 방법을 제시하였다. 더불어 현장 사용 성능과 관련한 상시진동 문제를 처리하기 위해 신호처리 및 고유진동수 추정법으로 FDD 방법이 채택되었다. 제안된 최소화 계측 시스템과 미러 주파수 개념의 특성 및 FDD 방법의 적용성을 보기 위하여 사장교 모형을 이용한 실험적 연구가 수행되었다. 실험 결과는 상시진동을 위한 FDD 방법이 최소화 시스템을 이용한 고유 진동수 판별에서도 효과적으로 잘 작동됨을 보여 주었다. 또한 미러 주파수 개념은 저속촬영에 따라 왜곡된 신호에서도 고주파수 영역에 있는 고유진동수 추정이 가능함을 보여 최소화 시스템의 한계돌파에 효과적임을 보여 주었다. 결론적으로 실험결과는 제안된 최소화 계측 및 신호처리 시스템이 상시진동 케이블 장력 추정에 효과적인 방법이 될 수 있음을 보여주었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권10호
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• pp.492-499
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• 2002

This paper presents the method for an estimation of discharge current waveform in short gap discharge by radiated electromagnetic fields. The method of current waveform estimation is to use the one antenna method (single field method) with a measured electric or magnetic field at given field point by a time domain antenna. In order to verify the availability of the estimation theory, the discharge current waveform estimation was performed by one antenna methods using the measured electric fields of Wilson & Ma and compared with experiments. In addition diagnosis technique for power equipments is able to prevent from large accidents by finding signs of tile accidents before they happen. From the results of the estimation of discharge current, we have a possibility for the application of insulation diagnosis technique for power equipments using S$F_6$ gas. From this point of view, this paper simulated discharge progress and partial discharge by using needle-plan electrodes system in S$F_6$, studied the distribution of frequency spectrum of the radiated electromagnetic waves using a biconical antenna and a spectrum analyzer. From the experimental results of this study, according to the consideration of the mutual relation between frequency spectrum of the radiated electromagnetic waves and discharge progress, it was confirmed that detecting Partial discharge and estimating discharge progress in S$F_6$ could be Possible.

• 대한전자공학회논문지SP
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• 제47권5호
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• pp.100-108
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• 2010

본 논문은 피치를 추출하는 방법으로 자기상관을 이용하였다. 시간과 주파수 영역의 자기상관은 서로 다른 특성을 가지고 있으며, 각각 피치주기와 기본주파수에 대응된다. 본 논문에서는 시간과 주파수 영역에서의 자기상관을 결합하는 방법을 이용하였다. 이 방법은 자기상관에서 발생하는 피치 doubling과 having 에러를 크게 개선시킬 수 있었다. 하지만, 시간과 주파수 영역에서 유성음의 주기적 특성인 피치주기와 기본주파수는 서로 역수 관계이며, 특히 기본주파수의 에러는 FFT의 분해능에 의하여 발생된다. 이러한 영향을 줄이기 위하여 시간 영역과 주파수 영역에서의 자기상관 결합에 보간법을 적용함으로써 피치 검출율을 향상 시킬 수 있었다. 자기상관을 결합할 때 시간영역에서 찾은 피치후보들에 대해서만 주파수영역의 자기상관을 구함으로써 계산량은 감축될 수 있었다. 또한, 선형보간을 이용하여 기존방법 보다 FFT 계수를 8배 줄일 수 있었다. 그 결과, FFT 연산량과 주파수영역의 자기상관 계산량을 크게 감축하여 기존 방법 대비 알고리즘 처리시간을 약 9.5배 줄일 수 있었다.

• The Journal of the Acoustical Society of Korea
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• 제24권4E호
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• pp.152-157
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• 2005

In this paper, a new data-aided joint phase and frequency estimator, which has very low computational complexity, is proposed and its variances of phase and frequency estimates are derived. To estimate the phase and frequency offset, first of all, the overall observation interval is divided into same length sub-intervals, and then phase estimates are independently computed based on symbols of the each sub-intervals. To be continue the sequence of computed phase estimates, proper integer multiples of $2{\pi}$ are added to (or subtracted from) the computed phase estimates, which is called linearized phase estimate. The phase offset of the proposed joint estimator is estimated by averaging the linearized phase estimates and the frequency offset by averaging the differences between consecutive linearized phase estimates. The variance of the proposed phase offset estimate is same to MCRB of phase if there is no frequency offset, but it is smaller than MCRB of phase if there is frequency offset. However, the variance of the proposed frequency offset estimate is bigger by at least 0.5 dB than MCRB of frequency with the same observation interval.