How to break a waveform waveform into its constituent harmonics using FFT and see the harmonic waveforms at each frequency?

I want to use Simulink to see the harmonics of a voltage waveform. So far I have used the fft simulink tool and only found the magnitude of the harmonic frequencies. What I would like to do is issolate and observe the waveform at the different frequencies as shown in the figure below.

[Mathieu NOE]

with the fft block you can get the fundamental frequency (or maybe you know it aleady before)

use that information to tune a bank of bandpass filters - each output correspond to one harmonic tone of the signal

Answer 1

[MULI]

Hi Rasula,

I understand that you need to isolate and observe the waveform at different harmonic frequencies of a voltage signal and you can follow the below steps to achieve this:

• First, convert your voltage signal to the frequency domain using the FFT block.
• Use a MATLAB Function block to zero out all frequency components except the one you want to observe.
• This allows you to isolate specific harmonics, such as the fundamental frequency, 3rd harmonic, etc.

function y = isolate_harmonic(X, harmonic_index) 
y = zeros(size(X)); 
y(harmonic_index) = X(harmonic_index);  % Retain only the desired harmonic 
end 

• Use the IFFT block to convert the frequency-domain data back to the time domain. This will give you the time-domain waveform of the isolated harmonic.

You can refer to these MathWorks documentation links for more information and examples related to “FFT” and “IFFT” block

https://www.mathworks.com/help/dsp/ref/fft.html

https://www.mathworks.com/help/dsp/ref/ifft.html

This method avoids the complex designs of bandpass filters for each harmonic.