How to find the FFT of a variable frequency sinusoidal signal in Simulink

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Haider 2024-3-8

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https://ww2.mathworks.cn/matlabcentral/answers/2092061-how-to-find-the-fft-of-a-variable-frequency-sinusoidal-signal-in-simulink

评论： Mathieu NOE 2024-3-11

I generated a sinusoidal signal with 3 frequencies (5, 10, 15 Hz) using the following method:

I tried to find the FFT of this signal with:

but the spectrum was nothing like what it's supposed to be, so what is the correct the way to find it (is the generating method correct or is there a better way)?

Thanks.

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Haider 2024-3-8

I tried using the fftshift, and I also replaced the clock with digital clock, but the results weren't better.

Mathieu NOE 2024-3-11

I haven't used this demo example, but it's purpose is to do a single fft computation for a fixed frequency signal

I suppose that you want to create multiple fft spectra for a variable frequency signal (as you would do to plot a spectrogram), so you have to change a bit the logic

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