dpienkow
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Hello Experts,
I am designing now the charge pump with phase detector for the PLL. At the moment I measure the phase noise at the output of the charge pump and observe the levels around -120 dBc @ 1kHz offset. Comparison frequency is 50 kHz. I do knot know, if it is good, very good or maybe poor result. Therefore, I would like to compare myself with state of the art circuit from National or Analog. They specify normalized phase noise for the PLL, which as far I understand should be the phase noise at the output of the charge pump.
To compute total noise of the closed loop PLL, both companies give the equation PNtotal=PNpll+10*log(Fcomp)+20*log(N),
where PNpll is what I am interested in.
This formula suggest, that decreasing the comparison frequency in my simulations will decrease the phase noise. It is not the case in my simulation. Therefore I would like to ask you, how to compute (simulate) this normalized phase noise?
Best Regards, Dariusz Pienkowski
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