• Title/Summary/Keyword: 고속 Fourier 변환방법

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Study of Radix-3 FFT (Radix-3 FFT에 관한 고찰)

  • Jung, Hae-Seung
    • Aerospace Engineering and Technology
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    • v.9 no.1
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    • pp.98-105
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    • 2010
  • Fast Fourier Transform is the fast implementation of Discrete Fourier Transform, which deletes periodic operation of DFT. According to the definition, radix-2 FFT can be implemented byre cursive call which divides the input signal points into 2 signal points. Because of its time-consuming stack-copy operation, this recursive method is very slow. To overcome this drawback, butterfly operation with signal rearrangement was devised. Based on the ideas of signal rearrangement and butterfly operation, this paper applies the signal rearrangement method to the Radix-3 FFT and checks the validity of this method.

Application of the modified fast fourier transformation weighted with refractive index dispersion far an accurate determination of film thickness (굴절률 분산을 반영한 고속 푸리에 변환 및 막두께 정밀결정)

  • 김상준;김상열
    • Korean Journal of Optics and Photonics
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    • v.14 no.3
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    • pp.266-271
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    • 2003
  • The reflectance spectrum of optical films thicker than a few microns shows an intensity oscillation due to interference. Since the spectral period of the oscillation is inversely related to film thickness, the thickness of an optical film can be determined from the spectral frequency of the oscillation. For rapid data processing, the spectral frequency is obtained by use of a Fast Fourier Transformation technique. The conventional method of applying a Fast Fourier Transformation to the reflectance spectrum versus photon energy is modified so as to clear the ambiguity in choosing the proper effective refractive index value and to prevent the broadening of the Fourier transformed peak due to the refractive index dispersion. This technique of modified Fast Fourier Transformation is suggested by the authors for the first time to their knowledge. From the analysis of the calculated reflectance spectrum of a 30-${\mu}{\textrm}{m}$-thick dielectric film. it is shown to improve the accuracy in determining film thickness by a great amount. The improved accuracy of the modified Fast Fourier Transformation is also confirmed from the analysis of the reflectance spectra of a sample with 80-${\mu}{\textrm}{m}$-thick cover layer and 13-${\mu}{\textrm}{m}$-thick spacer layer on a PC substrate.

A Simple Implementation of Dynamical Memory Allocation in Old-fashioned Singleton's Mixed-radix Fast Fourier Transformation Code (구식 싱글턴 혼합기수 고속푸리에변환 코드에 대한 간단한 동적메모리 할당방법 프로그래밍)

  • Kim, In-Gee
    • Journal of the Korean Magnetics Society
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    • v.22 no.2
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    • pp.33-36
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    • 2012
  • We propose a simple prescription for resolving the general-$N$ problem existing in the old-fashioned mixed-radix fast Fourier transformation FORTRAN subroutine by Singleton in 1968. After a brief investigation on the problem, we discuss our prescription with the worst case analysis within the dynamical allocation. The analysis reveals that our implementation is superior, at least for multi-variate data set, than previously proposed data copying methods.

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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Cover song search based on magnitude and phase of the 2D Fourier transform (이차원 퓨리에 변환의 크기와 위상을 이용한 커버곡 검색)

  • Seo, Jin Soo
    • The Journal of the Acoustical Society of Korea
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    • v.37 no.6
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    • pp.518-524
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    • 2018
  • The cover song refers to live recordings or reproduced albums. This paper studies two-dimensional Fourier transform as a feature-dimension reduction method to search cover song fast. The two-dimensional Fourier transform is conducive in feature-dimension reduction for cover song search due to musical-key invariance. This paper extends the previous work, which only utilize the magnitude of the Fourier transform, by introducing an invariant from phase based on the assumption that adjacent frames have the same musical-key change. We compare the cover song retrieval accuracy of the Fourier-transform based methods over two datasets. The experimental results show that the addition of the invariant from phase improves the cover song retrieval accuracy over the previous magnitude-only method.

N-Point Fast Fourier Transform Using 4$\times$4 Fast Reverse Jacket Transform (4-점 리버스 자켓 변환를 이용한 N-점 고속 푸리에 변환)

  • 이승래;성굉모
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.26 no.4B
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    • pp.418-422
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    • 2001
  • 4-점 리버스 자켓 변환 (4-Point Reverse Jacket transform)의 장점 중의 하나는 4-점 fast Fourier transform(FFT)시 야기되는 실수 또는 복소수 곱셈을 행렬분해(matrix decomposition)를 이용, 곱셈인자를 모두 대각행렬에만 집중시킨, 매우 간결하고 효율적인 알고리즘이라는 점이다. 본 논문에서는 이를 N 점 FFT에 적용하는 알고리즘을 제안한다. 이 방법은 기존의 다른 변환형태보다 확장하거나 구조를 파악하기에 매우 용이하다.

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Analusis of Strain Rate Distribution using Fourier Transform Grid Method (퓨리에 변환 격자법을 이용한 스트레인 속도분포의 해석)

  • 양인홍
    • Journal of the Korean Society for Precision Engineering
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    • v.10 no.4
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    • pp.135-141
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    • 1993
  • 고속으로 변형을 받는 재료의 변형 강도는 정적인 부하를 받는 경우와는 다르며 이 고속 현상을 해석하기 위해서는 시간적, 공간적 변화를 조사할 필요가 있다. 일반적으로 스트레인 속도를 구하는 데는 스트레인 게이지를 이용하고 있지만, 고무와 같은 대변형을 하는 물체에서는 정확한 데이터를 얻기가 곤란 하므로 스플라인 함수를 이용해서 보간 작업을 해야 한다. 그래서, 최근에는 스트레인 속도를 구하는 방법 으로 격자법, 모아레법, 광탄성법 등이 이용되고 있다. 재료의 변위 분포를 구하는 데는 격자법이 잘 이용 되어지고 있지만 스트레인 속도 분포의 해석의 정도에 문제가 되고 있다. 이러한 문제를 해결하기 위하여 본 논문에서는, 고속으로 변형하는 물체의 형상을 역학적으로 해석하기 위해 고속도 카메라로 촬영을 하고 그 때 얻어진 격자 화상을 퓨리에 변환 격자법을 이용해서 위상을 구하고 스트레인 속도 분포를 해석했다.

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Detection and Damping Recognition of Normal Frequency Using Fast Fourier Transform in the Vibration Acceleration Analysis System (진동가속도 분석시스템에서 고속푸리에변환을 이용한 기준진동수의 검출 및 감쇠인식)

  • Kim, Hwang Jun
    • Smart Media Journal
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    • v.8 no.2
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    • pp.16-20
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    • 2019
  • Fast Fourier Transform in the vibration acceleration analysis system has recently been utilized in the field of sensor measurement. In this paper, we propose a Fast Fourier Transform based method of detecting the normal frequency among the many frequency types of diffuse field. This normal frequency is expressed by the formula of frequency damping recognition which is calculated in a similar way to the octave center frequency. Based on this theory, this paper can more accurately inform noise producers of the degree of damping, which is different from the vibration type of diffuse field.

Range estimation of underwater acoustic moving source using Doppler frequency map (도플러 주파수 맵을 이용한 수중 이동 음원의 거리 추정)

  • Park, Woong-Jin;Kim, Ki-Man;Han, Min su;Choi, Jae-Yong
    • The Journal of the Acoustical Society of Korea
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    • v.36 no.6
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    • pp.413-418
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    • 2017
  • When measuring the radiated noise of an underwater vehicle, range information between acoustic source and receiver is an important evaluating factor, but it cannot use GPS. There is a method of using the cross correlation for finding the range of the acoustic source instead of the GPS. However, this method has heavy computational loads. This paper proposes a fast Fourier transform based method with a relatively small amount of computation to estimate the range of a source. The proposed method estimates Doppler frequencies of CW signals received at multiple receivers by fast Fourier transform and estimates the source range by comparing theoretical Doppler frequencies map previously calculated by a receiver position and source depth information. Simulation and lake trial were performed to verify the performance.

A Study on Multi Target Elevation Angle Estimation of Hight Directivity using Multi Stacked Beam Forming (다중 스택 빔 형성을 이용한 고 지향성의 다중 목표물 고각 추정에 대한 연구)

  • Lee, Kwan-Hyeong;Song, Woo-Young;Lee, Myung-Ho
    • Journal of the Korea Society of Computer and Information
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    • v.16 no.8
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    • pp.129-135
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    • 2011
  • In this paper, we propose a multi target's elevation angle estimation method using multi beam forming technique. This method make a stacked beam to digital processing a received signal in array element. There can be desired receiving beam to application weight value at antenna element in beam forming. Currently, we are to make multi stacked beam using fast fourier transform in stead of phase shifter to be a computer performance much improvement. Also, we improve multi beam directivity using beam steering error correction technique in order to beam steering to desired direction in receiver. Through simulation, we show that the proposed elevation estimation method based on fast fourier transform and beam steering error correction technique, improves th performance of target estimation compared to previous method.