horizon
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Posts: 16
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Hello Ken, Thank you a lot for your answer. I will use the strobe Pnoise analysis for my dividers. I still don't understand something...sorry...
You wrote > If you were to plot the noise power as a function of time during >a cycle, you would see that the noise would peak at the >transitions. So if you were to periodically sample the noise >during the transition, you would be sampling at the peak, and >the values in the resulting noise sequence would be large.
>If instead, you sampled the noise when the signal was either >high or low, the noise power in the sampled sequence would be >lower because there is less noise at that time.
So if the standard Pnoise analysis gives the average of the noise for one cycle. if there is a peak at a specific point and then something lower, the average of the noise should be lower than the noise given by the strobed Pnoise analysis. In the simulation it's the case.
but you wrote >However, if you look at the continuous time noise, you have to >consider the total noise power over the cycle. Here the noise at >the transition may contribute only a small amount to the total >noise power because the transition only lasts for a short period >of time. The power contributed while the output is stable (either >high or low) might be much greater even though its amplitude is >smaller because the output is stable for most of the cycle.
I thought the standard Pnoise analysis output was the average of the noise on one cycle ? Am I wrong ? In the previous text I copied from your post, I understand that the standard Pnoise output is giving the sum of the total noise and not the average.Is it the case ? If yes, I would like to get the phase noise of my divider in dBc. What I did is : I took the value given by the strobed analysis and I divide it by the power of my carier.
with standard Pnoise I get -162dBc with the strobed Pnoise I get -144.5dBc The is an huge difference, but I suppose I should take into account the -144.5dBc.
Than you again a lot for your time. Horizon
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