MATLAB: Phase between two waveforms

phasewaveforms

I'm trying to figure out the phase difference between two waveforms I downloaded from an oscilloscope. They are 1X2500 matricies. Here's the code I'm using (w1 and w2 are two waveforms I got from the oscilloscope with the getWaveform command)

CosTheta = dot(w1,w2)/(norm(w1)*norm(w2));
ThetaInDegrees = acosd(CosTheta)

This only gives me the absolute value of the phase. I don't know if it's negative or positive. How could I get this answer?

Thanks!

Best Answer

The sign of the phase depends on the waveform you use as the reference. The xcorr function could help you decide that.

EDIT — (15 Jul 2016 16:15 UTC)

They appear to be slightly different frequencies. They will never have a constant phase relationship.

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MATLAB: Solving nonlinear equations

I do get the following error message:

Error using solve>processString (line 337)
' -0.0889=(-w^0.5*(w-1)^2*(w*(w+2)*sinh(3*theta)+3*sinh(theta)))/(sqrt(2)*(w-1)*(w*cosh(2*theta)+1)^1.5) ' is not a valid expression or equation.

There seems to be a problem with theta. Since theta also is a MuPAD function, the symbolic engines confuses the input. If you have MATLAB 12a or later, you should try to avoid the string syntax (note, that you need double '==' for the comparison):

 syms w theta;
 eq1 = -0.0889==(-w^0.5*(w-1)^2*(w*(w+2)*sinh(3*theta)+3*sinh(theta)))/(sqrt(2)*(w-1)*(w*cosh(2*theta)+1)^1.5);
 eq2 = 7.2191 ==(w^2*((w^4+2*w^+3*w^2-3)*cosh(4*theta)+4*(w+2)*cosh(2*theta))+3*(2*w+1))/(2*(w*cosh(2*theta)+1)^2);
 [w theta]=solve(eq1,eq2,w,theta)

This gives:

w =
0.039410543092148572708570152224833
Theta =
1.5385135630436219217489780415314

If yo have an older version of MATLAB, try replacing theta by another variable. I tried Theta, with a capital T:

syms w Theta;
eq1 = '-0.0889=(-w^0.5*(w-1)^2*(w*(w+2)*sinh(3*Theta)+3*sinh(Theta)))/(sqrt(2)*(w-1)*(w*cosh(2*Theta)+1)^1.5)';
eq2 = '7.2191 =(w^2*((w^4+2*w^+3*w^2-3)*cosh(4*Theta)+4*(w+2)*cosh(2*Theta))+3*(2*w+1))/(2*(w*cosh(2*Theta)+1)^2)';
[w Theta]=solve(eq1,eq2,w,Theta)

MATLAB: How to simulate Constant Waveform (or PCW) signal generation using the Phased Array Toolbox 1.1 (R2011b)

Constant frequency waveforms may be implemented by using multiple ‘phased.RectangularWaveform’ system objects if there are multiple pulses of different frequencies which stay constant throughout the simulation. The frequency of each pulse being constant is implicit. A simple example demonstrating this is available at the following help page:

http://www.mathworks.com/help/releases/R2011b/toolbox/phased/ug/bssrbnv.html#bs7aui3

Best Answer

Related Solutions

MATLAB: Solving nonlinear equations

MATLAB: How to simulate Constant Waveform (or PCW) signal generation using the Phased Array Toolbox 1.1 (R2011b)

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