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a question about using cppsim to simulate PLL phase noise

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yfluo2004

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cppsim

Hi,

I am currently designing a PLL and using cppsim - PLL Design Assistant, to do the system simulation. When I simulate the PLL phase noise, I first specify the detector noise and VCO phase noise and then observe the PLL phase noise. I attached the phasenoise waveform. The setup for the detector noise is -90dBc/Hz; the VCO phase noise is -105dBc/Hz at 1MHz offset; the bandwidth is 3.88MHz with fz/fo=1/8.

Is the VCO phase noise the free running phase noise in the PLL Design Assistant setup window? Is the PLL phase noise supposed to be smaller than the VCO free running phase noise while here it seems the summation of the detector noise and phase noise? I am a little confused about that.
Could somebody give me some suggestions? Thanks a lot!

YLuo
 

free running vco phase noise

What is shown in the plot is the VCO's contribution to the loop and not it's free running noise. The free running VCO's noise will be much higher than the one shaped by the PLL's TF.
 

pll design assistant

Thank you, saro_k_82. Have you ever used the cppsim tool? Is there a way to show both free running vco phase noise and PLL phase noise in the same plot in PLL Design Assistant tool?
Thanks!

YLuo
 

cppsim

No I havent used that tool. To get the VCO noise, just multiply the closed loop VCO noise by the inverse of the appropriate TF.
 

cppsim phase noise

one question is how u get the detector 's phase noise
 

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