Hi，

I test the phase noise in my PLL based on ADF4159 and I don't know the relationship between the reference oscillator and the total PLL phase noise, could anyone tell me?

The normalized phase noise floor (PNsynth) contributes to the in-band phase noise of the PLL as the formula:

PN = PNsynth + 10Log(PFD) + 20Log(N), similarly, what is the formula for the reference oscillator ?

Thanks.

The reference noise inside the loop bandwidth is scaled up by 20 log (Fvco/Fref) = 20 log N. Near the loop bandwidth, where the response is affected by peaking, it may get scaled up more due to the loop feedback.

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