# Fourier series in Multisim

1. Sep 18, 2014

### etf

Is it possible to represent some signal in terms of Fourier series in Multisim? For example, Fourier series of sawtooth voltage with period T=2pi is $$\sum_{n=1}^{\infty }\frac{2}{n}(-1)^{n+1}sin{(nt)}=2sin{(t)}-sin{(2t)}+\frac{2}{3}sin{(3t)}-\frac{1}{2}sin{(4t)}+...$$. These terms on right side of equation will be AC voltage sources connected in series. For good approximation of sawtooth waveform I should use few hundreds terms of series. It would be impossible to connect all these sources manually :) Is there any better way to do this?

Last edited: Sep 18, 2014
2. Sep 18, 2014

### Baluncore

It would be easier to simulate a circuit that generates a linear sawtooth than to correctly phase and sum all those fourier terms.

3. Sep 18, 2014

### etf

I know there is sawtooth generator in Multisim but I used sawtooth waveform only as example. I was wondering is it possible to simulate random periodic signal which can be represented through Fourier series.

4. Sep 18, 2014

### Baluncore

How many different frequencies can Multisim generate at one time? One, or more?
How would you synchronise the phases to get the correct time domain signal?

5. Sep 20, 2014

### etf

I'm not sure I can give you right answer. If it's impossible in Multisim, can it be done in Simulink maybe? Here is my program in Matlab to plot Fourier series of sawtooth waveform:

clear
clc
t=linspace(0,2*pi,1000);
suma=0;
for n=1:10000
suma=suma+((2./n).*(-1).^(n+1)).*sin(n.*t);
end
plot(t,suma)
grid