# Problem using fft();

2 views (last 30 days)
atharva aalok on 21 Oct 2021
Commented: atharva aalok on 21 Oct 2021
I have a periodic signal with TimePeriod~2.3 that is f~.4347
But I am getting another peak at f = 0.
figure(1);
plot(tSol, omegaSol); % This is periodic with TimePeriod~2.3 or f~.4347
Fs = length(tSol) / (max(tSol)-min(tSol)); % Sampling frequency
T = 1/Fs; % Sampling period
L = Fs * (max(tSol) - min(tSol)); % Length of signal
t = (0:L-1)*T; % Time vector
Y = fft(omegaSol);
P2 = abs(Y/L);
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);
f = Fs*(0:(L/2))/L;
limit_f = f < 1;
f = f(limit_f);
P1 = P1(limit_f);
figure(2);
plot(f,P1)
title('Single-Sided Amplitude Spectrum of X(t)')
xlabel('f (Hz)')
ylabel('|P1(f)|') Why Is there another peak at f ~ 0?

KSSV on 21 Oct 2021
Edited: KSSV on 21 Oct 2021
Remove the mean from the data and then use fft.
Say A is your data, (array). For fft use:
A = A-mean(A) ;
atharva aalok on 21 Oct 2021
Yeah lol I just realised a second after posting thanks!

R2021a

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