how to get "fft" of sin wave?
2 visualizaciones (últimos 30 días)
Mostrar comentarios más antiguos
ADNAN KIRAL
el 24 de Jun. de 2019
Comentada: Star Strider
el 25 de Jun. de 2019
hi
I have the following code for "fft" but I could not get the exactly frequency-amplitude response. where did I make a mistake ? can u please help me with that?
I want to get this figure; amplitude 2.5 and frequency 4Hz.
final_point=3;
time=1:0.01:final_point;
omega=2*pi*4;
y1=2.5*sin(omega*time);
% %FFT
acc_inpt=y1;
n_fft=length(acc_inpt);
ff=fft(acc_inpt,n_fft);
num_points=n_fft;
ff=ff/(num_points/2);
figure;
plot(abs(ff))
0 comentarios
Respuesta aceptada
Star Strider
el 24 de Jun. de 2019
The amplitude appears to be correct. You need to define the frequency axis to get the frequencies to be correct:
final_point=3;
time=1:0.01:final_point;
omega=2*pi*4;
y1=2.5*sin(omega*time);
% %FFT
Fs = 1/mean(diff(time)); % Sampling Frequency
Fn = Fs/2; % Nyquist Frequency
Fv = linspace(0, 1, numel(y1)/2+1)*Fn; % Frequency Vector
Iv = 1:numel(Fv); % Index Vector
acc_inpt=y1;
n_fft=length(acc_inpt);
ff=fft(acc_inpt,n_fft);
num_points=n_fft;
ff=ff/(num_points/2);
figure;
plot(Fv, abs(ff(Iv)))
That plots the peak at 4 cycles/time unit, that appears to be what you want to do.
8 comentarios
Más respuestas (0)
Ver también
Categorías
Más información sobre Spectral Measurements en Help Center y File Exchange.
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!