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How to calculate Fourier transform (FFT), and Inverse FFT?

  1. 07-14-2018, 04:36 AM #1
    shamshersadiq
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    How to calculate Fourier transform (FFT), and Inverse FFT?

    Hi everyone,

    I have an acceleration time history, i want to calculate following
    1. Fast Fourier transform (FFT) of acceleration time history
    2. Again back calculation of time history by taking Inverse fourier transform (IFFT) of FFT.

    Please find the acceleration time history in attached excel sheet.

    Thanks
    excel_forum_FFT.xlsx
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  2. 07-14-2018, 04:45 AM #2
    AliGW
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    Re: How to calculate Fourier transform (FFT), and Inverse FFT?

    You are assuming that the wider membership will instantly know what FFT is and how to calculate it. That is quite an assumption!

    Please tell us mathematically how FFT and IFFT would be calculated, then we can help you build a formula.
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  3. 07-14-2018, 04:53 AM #3
    AliGW
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    Re: How to calculate Fourier transform (FFT), and Inverse FFT?

    Well, I found this: http://www.dspguide.com/ch12/2.htm

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  4. 07-14-2018, 06:00 AM #4
    Glenn Kennedy
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    Re: How to calculate Fourier transform (FFT), and Inverse FFT?

    Thats sooo much clearer now....

    here's a setp-by-step guide from researchgate

    https://www.researchgate.net/post/ho...sform_on_excel

    and a pdf
    Attached Files Attached Files
    Last edited by Glenn Kennedy; 07-14-2018 at 06:03 AM.
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  5. 08-03-2023, 02:32 PM #5
    Chornomor
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    Re: How to calculate Fourier transform (FFT), and Inverse FFT?

    You can use this formula to calculate FFT directly.

    Formula: copy to clipboard 
    Please Login or Register  to view this content.


    You should create workbook name like "FFT", copy and paste the formula above as range of name and use it as ordinary formula in cells with two parameters. First is a data array and the second is a boolean value that indicate direct or inverse form of transform you need. Your data size should be 2k of complex numbers. See attachment for example.

    You should have one of the last version of Excel with dynamic array support.

    excel_forum_FFT.xlsx
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  6. 08-03-2023, 03:14 PM #6
    MrShorty
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    Re: How to calculate Fourier transform (FFT), and Inverse FFT?

    For an older version of Excel, you may find the information in this thread useful: https://www.excelforum.com/excel-pro...ft-in-vba.html
    Quote Originally Posted by shg
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