how to make fft of rectangular function?

Ts = 0.01; N=2000; t=-20:Ts:(N-1)*Ts; T = 1; fs=1/Ts; f=0:fs/N:(N-1)/N*fs; x1 = rectpuls(t, T); xk=fft(x1); figure(1); plot(t,x1); figure(2); plot(0:N-1, xk); figure(3); plot(f, 1/N*abs(xk));

figure1,2 are not found. what is the problem? how can i fix it?

Answer 1

[Star Strider]

Small error in figure(3). You do not need figure(2).

This works:

Ts = 0.01; N=2000; t=-20:Ts:(N-1)*Ts;
T = 1;
fs=1/Ts;
f=0:fs/N:(N-1)/N*fs;
x1 = rectpuls(t, T);
xk=fft(x1);
figure(1); plot(t,x1)2
figure(3); plot(f, 1/N*abs(xk(1:length(f))));

[YEON HWEE BAE]

thank you so much ^^

[Star Strider]

My pleasure.

If my Answer helped you solve your problem, please Accept it!

[Parth Patel]

In this program , i asume, f = frequency.

can the value of frequency be zero?

f=0:fs/N:(N-1)/N*fs;

thanks in adavnce

[Star Strider]

Yes.

A zero frequency signal is d-c, usually present as a constant offset in a signal that is otherwise varying. The d-c component is the mean of the signal.

Answer 2

[Tilkesh]

function y = rect(x, D)

% function y = rect(x, D)

if nargin == 1, D = 1;

x = abs(x);

y = double(x<D/2);

y(x == D/2) = 0.5;

end