1alph1
Newbie level 2
multiplication fft
Hey everyone, first of all id just like to clarify this isnt a homework or coursework related problem, its part of my personal MatLab learning for future years. I obtained a nice little siganls and systems question off a friend, it looked fairly simple but ive come across a problem which i cant find a solution to. Here goes...
Investigate the frequency content X(f) of a single 10 Hz sinewave, lasting for a time T_end. Set the sample frequency to be fs=1000, and T_end to be 2. Plot the absolute value of the function X(f) as a against frequency f.
Here is my code for this part.
I believe this to be correct, and can explain the results obtained at different T_end values.
The next part of the question is where I get stuck.
Replace the line that defines x(t) with the code,
in order to create a pulse of length 1.
When this code is entered i get the standard, Error using ==> times
Matrix dimensions must agree.
Error in ==> sinwav at 9
x(1:length(t1))=sin(2*pi*f*t1);
I know this error occurs due to matrix multiplication, but simply .*'ing does not solve it,
the matrix sizes are apparaently as follows, x[1 x 2000] , t1[1 x 1000], t[1x2000],f[1 x 2000]. And im not actually sure if i should add the .'s and this would change the outcome.
Im not sure why the value for t is a 1 by 2000 matrix, im sure it should only be a 1000.
Any comments or information would be greatly appericated, and hopefully this will help others as well.
Many Thanks
Hey everyone, first of all id just like to clarify this isnt a homework or coursework related problem, its part of my personal MatLab learning for future years. I obtained a nice little siganls and systems question off a friend, it looked fairly simple but ive come across a problem which i cant find a solution to. Here goes...
Investigate the frequency content X(f) of a single 10 Hz sinewave, lasting for a time T_end. Set the sample frequency to be fs=1000, and T_end to be 2. Plot the absolute value of the function X(f) as a against frequency f.
Here is my code for this part.
Code:
function [x, t] = sinewave(T_end)
fs = 1000;
ts = 1/fs;
T = T_end;
t = 0:ts:T_end-ts;
f= -fs/2 : 1/T : fs/2-1/T; % sets the frequecncy axis, between -500 and (500-0.5).
x = sin(2.*pi.*f.*t);
X = fft(x);
Y = fftshift(X); % shifts right hand end to its alias below f=0, as graph is periodic this just centers the plot about 0.
stem(f,abs(Y),'k')
xlabel('frquency Hz');
ylabel('Abs(X)');
title('frequency content at T end = 2');I believe this to be correct, and can explain the results obtained at different T_end values.
The next part of the question is where I get stuck.
Replace the line that defines x(t) with the code,
Code:
t1= 0:ts:1.0-ts;
x=0*t;
x(1:length(t1))=sin(2*pi*f*t1);
figure(1)
plot(t,x)
figure(2)in order to create a pulse of length 1.
When this code is entered i get the standard, Error using ==> times
Matrix dimensions must agree.
Error in ==> sinwav at 9
x(1:length(t1))=sin(2*pi*f*t1);
I know this error occurs due to matrix multiplication, but simply .*'ing does not solve it,
the matrix sizes are apparaently as follows, x[1 x 2000] , t1[1 x 1000], t[1x2000],f[1 x 2000]. And im not actually sure if i should add the .'s and this would change the outcome.
Im not sure why the value for t is a 1 by 2000 matrix, im sure it should only be a 1000.
Any comments or information would be greatly appericated, and hopefully this will help others as well.
Many Thanks