What kind of loop filter preferred in frequency synthesizer?

[Adam2008]

I am designing a frequency synthesizer of 2.5GHz, what kind of loop filter preferred in it?


Thanks!

 

[Eugen_E]

Re: What kind of loop filter preferred in frequency synthesi

The system is usually 2nd order, so the stability is easily predicted. The PD would use a charge pump, so the filter will be RC series. To improve the reference rejection, a small capacitor, C/10 is connected in parallel to the resistor. This reduces a bit the phase margin but greatly reduces the reference leakeage.

The software from Analog Devices permits a more complex design, with higher performance.
ADI Sim PLL
http://forms.analog.com/form_pages/rfcomms/adisimpll.asp