# How to align multiple signals?

47 vues (au cours des 30 derniers jours)
Susan le 7 Fév 2023
Hi Matlab experts,
I'm trying to align these signals but have yet to be successful.
The signals are attached. They are periodic, noisy sin signals. I used the alignsignals function as well as xcorr to align the signals. Could somebody help me out with that?
Moreover, how can I compute the frequency of these signals?
##### 0 commentairesAfficher -1 commentaires plus anciensMasquer -1 commentaires plus anciens

Connectez-vous pour commenter.

### Réponse acceptée

Sulaymon Eshkabilov le 8 Fév 2023
Here is one of the viable solutions to compute resonant frequencies of each signal and find out if their are coherent:
fs = 1024;
S = [S1; S2; S3; S4; S5; S6];
N = length(S1);
freq = fs*(0:(N/2))/N; % Freq values
for ii=1:6
Y = fft(S(ii,:), N); % FFT of the signal s(t)
Yp = abs(Y/N); % Absolute value or magnitude of the signal spectrum
semilogy(freq,Yp(1:N/2+1), 'linewidth', 2)
hold all
end
title('FFT analysis of a signal')
xlabel('Frequency, [Hz]')
ylabel('Magnitude of signal = |S(f)|')
ylim([0, 0.025])
legend({'s1', 's2', 's3', 's4', 's5', 's6'})
grid on
You can check signal coherences using wcoherence() function:
wcoherence(S1,S2)
wcoherence(S2,S3)
wcoherence(S3,S4)
wcoherence(S4,S5)
wcoherence(S5,S6)
It looks like signal s5 and s6 are pure noise.
##### 2 commentairesAfficher 1 commentaire plus ancienMasquer 1 commentaire plus ancien
Sulaymon Eshkabilov le 8 Fév 2023
Modifié(e) : Sulaymon Eshkabilov le 8 Fév 2023
Most welcome. What do mean to align the signals in the time domain? Put them together or what? to make their peak values correspond?
You can try alignsignals() fcn:
[S2a, S3a] = alignsignals(S2, S3, [], "truncate");
nexttile
plot(S2), hold on
plot(S3)
nexttile
plot(S2a), hold on
plot(S3a)
hold off
See - DOC.

Connectez-vous pour commenter.

### Plus de réponses (1)

Sulaymon Eshkabilov le 7 Fév 2023
One fundamental question for signal processing is a "must", that is "what is the data sampling time or sampling frequency?"
Pl., provide this info.
##### 1 commentaireAfficher AucuneMasquer Aucune
Susan le 7 Fév 2023
Modifié(e) : Susan le 7 Fév 2023
@Sulaymon Eshkabilov Thanks for your response. The sampling rate of all signals equals 1024.

Connectez-vous pour commenter.

### Catégories

En savoir plus sur Descriptive Statistics 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!

Translated by