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Exportation Phase Noise Trace and Plotting in Matlab

Question asked by svia on Nov 24, 2009
Latest reply on Nov 25, 2009 by DaveHornbeck
Hello, I hope you can help me with this question, please.

I have a free-running oscillator, and I measured its phase noise using the VSA.
I read some points using the marker in this trace:
These values, as far as I understand, are double side band.
1002MHz..............-115.843
600KHz................-112.259
402KHz...............-107.76

Then I exported the trace and save it in .mat file.

I wrote a simple script to plot it.

load ('oscilator_phasenoise_12G406.mat')
X_osc=(XStart:XDelta:FreqValidMax);
Y_osc=Y(1:length(X_osc));
SSB=0;
semilogx(X_osc,(10*log10(Y_osc)-SSB),'r')


SSB=0; that means that I Intend to plot double side band results. I supose that  Y vector I've got after exporting are double side band values.

Doing that, I see that there is a difference of 3dB between the values read by the marker, and the values plotted by me in Matlab.

Example: 1002MHz---- trace -115.84-----plot -112.8

My question is:
-     How to plot the results in Matlab,
-     Y trace exported is single or double band values
-     Taking into account that L(f) single band, Sp(f) double band, and L(f)=Sp(f)-3dB [1], single side values should be reached subtracting  Y-3dB.

I include the .mat file, and an image of VSA.

Please, if I was not clear, ask me as much as you wish, I really need an answer. Thank you.
[1]     E.S. Ferre-Pikal, J.R. Vig, J.C. Camparo, L.S. Cutler, L. Maleki, W.J. Riley, S.R. Stein, C. Thomas, F.L. Walls, and J.D. White : "Draft revision of IEEE STD 1139-1988 standard definitions of physical quantities for fundamental frequency and time metrology - Random instabilities". IEEE International Frequency and Control Symposium, 1997, (pp338-357)  

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