• Title, Summary, Keyword: Fast Fourier Transform Filter

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A Comparison between Abel-Fourier and Digital Linear Filter Methods (Abel-Fourier법과 디지탈 선형필터법과의 비교)

  • Kim, Hee Joon
    • Economic and Environmental Geology
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    • v.20 no.2
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    • pp.119-123
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    • 1987
  • Hankel transform of order 0 can be represented by a combination of Abel transform and Fourier transform. This Abel-Fourier method can offer computational advantages over a conventional digital linear filter method through the uses of a rapid Abel transform with shift variant recursive filter and of a fast Fourier transform. The Abel-Fourier method, however, is generally less accurate than a well-designed digital linear filter method. In geoelectrical applications, the digital linear filter method seems to be more flexible than the Abel-Fourier method.

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Enhanced Startup Diagnostics of LCL Filter for an Active Front-End Converter

  • Agrawal, Neeraj;John, Vinod
    • Journal of Power Electronics
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    • v.18 no.5
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    • pp.1567-1576
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    • 2018
  • The reliability of grid-connected inverters can be improved by algorithms capable of diagnosing faults in LCL filters. A fault diagnostic method during inverter startup is proposed. The proposed method can accurately generate and monitor information on the peak value and the location of the peak frequency component of the step response of a damped LCL filter. To identify faults, the proposed method compares the evaluated response with the response of a healthy higher-order damped LCL filter. The frequency components in the filter voltage response are first analytically obtained in closed form, which yields the expected trends for the filter faults. In the converter controller, the frequency components in the filter voltage response are computed using an appropriately designed fast Fourier transform and compared with healthy LCL response parameters using a finite state machine, which is used to sequence the proposed startup diagnostics. The performance of the proposed method is validated by comparing analytical results with the simulation and experimental results for a three-phase grid-connected inverter with a damped LCL filter.

Design of the fast adaptive digital filter for canceling the noise in the frequency domain (주파수 영역에서 잡음 제거를 위한 고속 적응 디지털 필터 설계)

  • 이재경;윤달환
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.41 no.3
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    • pp.231-238
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    • 2004
  • This paper presents the high speed noise reduction processing system using the modified discrete fourier transform(MDFT) on the frequency domain. The proposed filter uses the linear prediction coefficients of the adaptive line enhance(ALE) method based on the Sign algorithm The signals with a random noise tracking performance are examined through computer simulations. It is confirmed that the fast adaptive digital filter is realized by the high speed adaptive noise reduction(HANR) algorithm with rapid convergence on the frequency domain(FD).

The orthogonal filter design using improved fast Walsh transform (개선된 고속월쉬변환에 의한 직교필터 설계)

  • Chung, Je-Wook;Cho, Young-Ho;Lee, Han-Seok;Park, Jun-Hoon;Shim, Jae-Sun;Ahn, Doo-Soo
    • Proceedings of the KIEE Conference
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    • pp.2620-2623
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    • 2000
  • The standard approach consists of using correlation of orthogonal functions in digital filtering, such as well-known FFT(Fast Fourier Transform) and FWT(Fast Walsh Transform). But it needs much calculations, multiplications and additions. The calculation amount is m $log_2m$ in the general case. Therefore, this requires high speed processors to calculate in real time, which can calculate floating point. This study developed improved fast Walsh transform based on dyadic-ordered fast Walsh transform, then regenerated signal flow graph of improved fast Walsh transform, and used it for digital filtering, and then measured fundamental frequency and harmonics for current and voltage signals of power system.

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Spectral Analysis of the ECG Using the Improved ARMA FTF Algorithm (개선된 ARMA FTF 알고리즘을 이용한 ECG 신호의 스펙트럼 해석)

  • Nam, Hyeon-Do;An, Dong-Jun;Lee, Cheol-Hui
    • Journal of Biomedical Engineering Research
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    • v.15 no.4
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    • pp.395-400
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    • 1994
  • High resolution spectral analysis is essential for ECG anaysis. The fast Fourier transform has been widely used for frequency analysis of ECG signals but this procedure provides poor resolution when the data record is short and shows Gibb's phenomena. The ARMA FTF (Fast Transversal Filter) algorithm is used for high resolution spectral analysis. The reason of unsalability of this algorithm is investigated and the method for improving the numerical stability is proposed. The proposed algorithm is applied to spectral analysis of the ECG. Since this result has less variations than the FFT based results, it can be used for the computerized diagonosis of the ECG.

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Analysis of the Ocean Acoustic Channel Using M-sequences in Ocean Acoustic Tomography (해양 음향 토모그래피에서 M-시퀀스를 이용한 해양 음향 채널 분석)

  • Seo, Seok;Lee, Chan-Kil
    • The Journal of the Acoustical Society of Korea
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    • v.23 no.1
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    • pp.24-29
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    • 2004
  • In ocean acoustic tomography (OAT), the pulse compression techniques using M-sequences are employed in the many studies for investigating the ocean structures. M-sequences can provide the good time and Doppler resolution in the process of demodulation using matched-filter. The signal-to-noise (SNR) performance at the output of receiver may be improved by manipulating received signal, i. e. coherently averaging. The processing time can be significantly reduced by using fast hadarmard transform (FHT) or fast Fourier transform (FFT). In this paper, we estimate the multipath arrival structures and delay times using the East Korean Sea experiment data and explore the compensation method for the detrimental effects on performance due to sampling rate error. We also analyze the characteristics of the ocean acoustic channels through scattering function, delay power profile, and time dispersions.

Estimation of Total Sound Pressure Level for Friction Noise Regarding a Driving Vehicle using the Extended Kalman Filter Algorithm (확장형 칼만필터 알고리즘을 활용한 차량 주행에 따른 마찰소음의 총 음압레벨 예측)

  • Dowan, Kim;Beomsoo, Han;Sungho, Mun;Deok-Soon, An
    • International Journal of Highway Engineering
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    • v.16 no.5
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    • pp.59-66
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    • 2014
  • PURPOSES : This study is to predict the Sound Pressure Level(SPL) obtained from the Noble Close ProXimity(NCPX) method by using the Extended Kalman Filter Algorithm employing the taylor series and Linear Regression Analysis based on the least square method. The objective of utilizing EKF Algorithm is to consider stochastically the effect of error because the Regression analysis is not the method for the statical approach. METHODS : For measuring the friction noise between the surface and vehicle's tire, NCPX method was used. With NCPX method, SPL can be obtained using the frequency analysis such as Discrete Fourier Transform(DFT), Fast Fourier Transform(FFT) and Constant Percentage Bandwidth(CPB) Analysis. In this research, CPB analysis was only conducted for deriving A-weighted SPL from the sound power level in terms of frequencies. EKF Algorithm and Regression analysis were performed for estimating the SPL regarding the vehicle velocities. RESULTS : The study has shown that the results related to the coefficient of determination and RMSE from EKF Algorithm have been improved by comparing to Regression analysis. CONCLUSIONS : The more the vehicle is fast, the more the SPL must be high. But in the results of EKF Algorithm, SPLs are irregular. The reason of that is the EKF algorithm can be reflected by the error covariance from the measurements.

Robust Speech Endpoint Detection in Noisy Environments for HRI (Human-Robot Interface) (인간로봇 상호작용을 위한 잡음환경에 강인한 음성 끝점 검출 기법)

  • Park, Jin-Soo;Ko, Han-Seok
    • The Journal of the Acoustical Society of Korea
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    • v.32 no.2
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    • pp.147-156
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    • 2013
  • In this paper, a new speech endpoint detection method in noisy environments for moving robot platforms is proposed. In the conventional method, the endpoint of speech is obtained by applying an edge detection filter that finds abrupt changes in the feature domain. However, since the feature of the frame energy is unstable in such noisy environments, it is difficult to accurately find the endpoint of speech. Therefore, a novel feature extraction method based on the twice-iterated fast fourier transform (TIFFT) and statistical models of speech is proposed. The proposed feature extraction method was applied to an edge detection filter for effective detection of the endpoint of speech. Representative experiments claim that there was a substantial improvement over the conventional method.

3-D Surface Profile Measurement Using An Acousto-optic Tunable Filter Based Spectral Phase Shifting Technique

  • Kim, Dae-Suk;Cho, Yong-Jai
    • Journal of the Optical Society of Korea
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    • v.12 no.4
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    • pp.281-287
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    • 2008
  • An acousto-optic tunable filter based 3-D micro surface profile measurement using an equally spaced 5 spectral phase shifting is described. The 5-bucket spectral phase shifting method is compared with a Fourier-transform method in the spectral domain. It can provide a fast measurement capability while maintaining high accuracy since it needs only 5 pieces of spectrally phase shifted imaging data and a simple calculation in comparison with the Fourier transform method that requires full wavelength scanning data and relatively complicated computation. The 3-D profile data of micro objects can be obtained in a few seconds with an accuracy of ${\sim}10nm$. The 3-D profile method also has an inherent benefit in terms of being speckle-free in measuring diffuse micro objects by employing an incoherent light source. Those simplicity and practical applicability is expected to have diverse applications in 3-D micro profilometry such as semiconductors and micro-biology.

Analysis of Hertzian Contact using Fast Fourier Transform (FFT를 이용한 Hertz Contact 해석)

  • 구영필;조용주
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.131-138
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    • 1998
  • In this study, a numerical procedure to solve a contact problem has been developed. The procedure takes the advantage of signal processing technique in frequency domain to achieve the shorter computer processing time. The Boussinesq's equation was adopted as the response function. This procedure is applicable to the non-periodic surface profile as well as the periodic one. The validity of this procedure has been established by comparing the numerical results with the exact solutions. The effectiveness of this procedure is lied on the shorter computing time than any other contact analysis algorithm.

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