Power spectral density of IMF's for EMD and VMD

Hello everyone,

I am using EMD and VMD for my signals. I have plotted the IMF's graphics. Also, I want to plot individually PSD depends on frequencies. How can I plot it?

Regards

[Jiayi]

Hello, have you solved the problem? I have the same issue that needs to be solved. If you have solved it, I hope to help me solve it, good luck.

Answer 1

[Balavignesh]

Hi Fatih,

As per my understanding, you would like to plot Power Spectral Densities (PSD) of each Intrinsic Mode Function (IMF) obtained from Empirical Mode Decomposition (EMD) or Variational Mode Decomposition (VMD).

I am assuming you have already obtained the IMF's from EMD or VMD.

I suggest you to use the MATLAB function 'pwelch' to calculate the PSD.

In that case, the following example code may help you understand this:

% Sample IMF's. Input the calculated IMF
imf1 = sin(2*pi*10*(0:0.01:1))';% A sinusoidal signal with frequency 10 Hz
imf2 = randn(1, 101)'; % Random noise signal
imf3 = chirp(0:0.01:1, 5, 1, 20)'; % A linearly frequency-modulated (chirp) signal

% Sample value for segment length
segmentLength = 101; % Choose an appropriate segment length based on your signal characteristics and desired frequency resolution
imfs = [imf1 , imf2 , imf3]; 

% Set the sampling frequency and segment length for PSD calculation
fs = 50; % Sampling frequency of the signal


% Calculate and plot the PSD for each IMF
numIMFs = size(imfs, 2);

for i = 1:numIMFs
    % Calculate the PSD using Welch's method
    [psd, freq] = pwelch(imfs(:, i)', hamming
(segmentLength) ,[] ,[], fs);

    % Plot the PSD
    subplot(numIMFs, 1, i);
    plot(freq, 10*log10(psd));
    xlabel('Frequency (Hz)');
    ylabel('Power Spectral Density (dB/Hz)');
    title(['PSD of IMF ', num2str(i)]);
end

Please refer to the following documentation links to have more information on:

• 'pwelch' function: https://www.mathworks.com/help/signal/ref/pwelch.html
• 'hamming' function: https://www.mathworks.com/help/signal/ref/hamming.html