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https://designers-guide.org/forum/YaBB.pl Design >> RF Design >> phase noise time/freq domain simulation prob. https://designers-guide.org/forum/YaBB.pl?num=1165368339 Message started by Aigneryu on Dec 5th, 2006, 5:25pm |
Title: phase noise time/freq domain simulation prob. Post by Aigneryu on Dec 5th, 2006, 5:25pm Dear all, Right now I am confused by the time domain noise simulation for phase noise. I setup is that I only compute the phase noise at 1MHz offset All voltage is taken as differential signal. I first plot 3 items: phase noise, the I plot the output noise, and the rms spectrum of the signal. It agrees that phase noise = 20*log10(pnoise output noise in V/sqrt(Hz) / PSS differential rms voltage ) = 20*log10(pnoise output noise in V/sqrt(Hz) / PSS differential peak voltage ) + 3dB And I switched to time domain noise simulation, also only compute 1MHz offset. Then I get a noise power over an oscillation cycle. I take the average power, and divided by the sqaure of the rms PSS amplitude. 10*log10(tdnoise average power in V^2/Hz) - 20*log10(PSS differential rms voltage), and this number is 3dB higher then the previous phase noise result at 1MHz offset. So it turns out to be that: phasenoise = 10*log10(tdnoise/2 in V^2/Hz) - 20*log10(PSS differential rms voltage) = 10*log10(tdnoise/2 in V^2/Hz) - 20*log10(PSS differential peak voltage) + 3dB Rather than simply use the average power, an extra 0.5 factor should be added. I do not have any idea about it. Did anybody experienced the similar problem? |
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