Why do my amplitude become wrong when I vary the frequency from int to double?
1 vue (au cours des 30 derniers jours)
Afficher commentaires plus anciens
So I started with this code:
A = 10;
B= 17.6;
C=2;
D=11.2;
phi1 = 2;
phi2 = 5;
phi3 = 1;
phi4 = 0;
Fs = 100;
t = 0:1/Fs:1-1/Fs;
x=A*sin(2*pi*10*t+phi1)+B*cos(2*pi*5*t+phi2)+C*sin(2*pi*2*t+phi3)+D*cos(2*pi*t+phi4);
xdft = fft(x);
magnitude = 2* abs(xdft)/length(x)
phase = angle(2* max((xdft))/length(x))
And that gave me all the amplitudes exactly. However when say I change the first frequency from A*sin(2*pi*10*t+phi1) to A*sin(2*pi*10.5*t+phi1), it goes crazy and give me weird output... what am I doing wrong?
Thank you
0 commentaires
Réponses (1)
Wayne King
le 19 Fév 2013
It does not go "crazy", it only gets the amplitude wrong for the frequency f = 10.5 and this is problem I explained to you in the other post. 10.5 does not correspond to a DFT bin.
See
Voir également
Catégories
En savoir plus sur Spectral Measurements dans Help Center et File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!