What is an efficient way to calculate the FFT of a signal at specific

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Jalal-ad-din - 2021-03-12T10:57:19+00:00
Question: What is an efficient way to calculate the FFT of a signal at specific

What is an efficient way to calculate the FFT of a signal at specific frequency points in Signal Processing Toolbox 6.12 (R2009b) ? Normally, the FFT function returns the frequency response of a signal at regularly spaced frequency points given by the equation:     f = kFs/N where k is given by the vector [0:N-1] N is the length of the input signal vector Fs is the sampling frequency However, I am only interested in specific frequency points. Is there an efficient way of calculating the frequency response of a signal at irregularly spaced frequency points?  

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    • Expert Answer

    Profile picture of John Michell John Michell answered . 2025-11-20

    In Signal Processing Toolbox 6.12 (R2009b), the GOERTZEL function is an efficient way of calculating the frequency response of a signal at specific frequency points.
     
    This function uses the second-order Goertzel algorithm which computes DFT values at a specified subset of indices. If less than log2(N) points are required, GOERTZEL is more efficient than the Fast Fourier Transform (FFT).


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