Matlab code for square wave generation from fourier series (symsum fails for upperlimit greater than 1000 in my case)

function [a0,An,Bn]=mysquare(T,N)

syms t n

w0=2*pi/T;

a0=1/T*(int(1,t,0,T/2));

an=2/T*(int(1*cos(n*w0*t),t,0,T/2));

bn=2/T*(int(1*sin(w0*n*t),t,0,T/2));

An=symsum(an.*cos(n*w0*t),n,1,N);

Bn=symsum(bn.*sin(n*w0*t),n,1,N);

%main script

T=4;

[a0,an,bn]=mysquare(T,10000);

ft=a0+an+bn;

fplot(ft);

This works fine for N<=1000 but for larger values it takes alot of time and no result.

Answer 1

[Charan Jadigam]

Hi,

The function 'symsum' is trying to find a closed form expression as an answer and it is unable to do so.

Instead, as a workaround, use ‘sum’ function to solve the equation. The usage in your example would be,

An=sum(subs(an.*cos(n*w0*t),n,1:10000));
Bn=sum(subs(bn.*sin(n*w0*t),n,1:10000));

[Rishav Raj]

Yes that solved my problem thanks alot!