How to know which Signal is delayed !

Question

Susan 2011-8-22

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/14204-how-to-know-which-signal-is-delayed

Dear all, I have my code below for real data samples. I already tested the xcorr delay calculation method with different data and it produced the right answer but with the real data, I am not sure how to know after calculating the delay which of the two signal is the delayed version of the other?

x = sample1(:,1);
X = (x).';
y = sample2(:,1);
Y = (y).';
figure;
clf
subplot(3,1,1);
[xi,f]=ksdensity(X); 
plot(f,xi); 
line(repmat(X,2,1),repmat([0;0.1*max(xi)],1,length(X)),'color','r' ); 
subplot(3,1,2);
[xi,f]=ksdensity(Y); 
plot(f,xi); 
line(repmat(Y,2,1),repmat([0;0.1*max(xi)],1,length(Y)),'color','r' );
[Rxx,lags] = xcorr(X,Y);
[Z,delay] = max(Rxx);
lags(delay);

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Answer 1

Fangjun Jiang 2011-8-22

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https://ww2.mathworks.cn/matlabcentral/answers/14204-how-to-know-which-signal-is-delayed#answer_19465

在 MATLAB Online 中打开

Susan, Others don't have your data sample1 and sample2 so won't be able to look at your data. Would the sign of lags(delay), be positive or negative, tell you whether Y is the delay of X, or X is the delay of Y?

In my answer to your previous question, http://www.mathworks.com/matlabcentral/answers/13110-signal-processing

y is 10 steps lag behind x, when running

[Rxx, lags] = xcorr(x, y);
[Y, I] = max(Rxx);
lags(I)

It returns -10, meaning y is 10 steps lag behind x

If you run

[Rxx, lags] = xcorr(y, x);%switch order of x and y
[Y, I] = max(Rxx);
lags(I)

It returns 10, meaning x is 10 steps ahead of y

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Fangjun Jiang 2011-8-23

You could visually inspect your data to get a sense whether the result is in the ballpark.

Susan 2011-8-23

It would not be accurate but the fact that swapping both x,y gives different results I think its a sign the delay calculated is not right.. Any idea where I am going wrong?

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