I would like to view code that i can type in order to simulate all harmonics of a simple sine wave within matlab. Thank you.

I would like to perform harmonic analysis on a sine wave and see their distribution as the multiples increase in magnitude of a 50Hz 400V sine wave. Please help.

Answer 1

[Walter Roberson]

Sample code.

 fig = figure('Units', 'normal', 'Position', [0 0 .9 .9]);

 f0 = 50;        %50 Hz
 T = 1;          %for 1 seconds. Can be less than 1
 FS = 500;       %sampled at 500 Hz

 hL = floor(T/2*FS);   %half length
 samp_per_Hz = f0*T;

 H0 = 1;         %power of fundamental

 for H1 = linspace(0,5);   %progression of first harmonic
   f = zeros(1, hL);
   f(floor(samp_per_Hz)) = H0;
   f(floor(2*samp_per_Hz)) = H1;
   w = [0, f, fliplr(f)];   %symmetric with 0 power
   y = ifft(w);
   t = (0:length(w)-1)/FS;
   plot(t, y);
   pause(0.1);
 end

Your FS (sampling frequency) needs to be at least twice your fundamental. The higher you raise your FS the more points it will need to fit across the axes and so the closer together the peaks will get; but at the same time the higher the FS the smoother the curves (especially when you zoom.)

[Rebecca Bisangwa]

okay thank you very much.

[Rebecca Bisangwa]

by the way what are the axes values that you used? because I think I would like to plot an amplitude vs frequency graph for this one. So should I just use FFT?

[Walter Roberson]

The x axes is time in seconds. The y axes is, I guess, power per frequency, but not in decibels (see http://www.mathworks.com/help/signal/ug/psd-estimate-using-fft.html?BB=1)

Amplitude vs frequency would be

plot(w);

in its anti-symmetric form, or you could fftshift(w) to put frequency 0 (DC component) at the center. Labeling the x axes on such plots is always a nuisance.