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ADF4350 Setup Suggestions

Question asked by Subby on Sep 25, 2013
Latest reply on Sep 26, 2013 by rbrennan

Hi,

 

I am using an ADF4350 as LOs in a radio link at 2401.7 MHz.  What would be the suggested setup for such a frequency using a Ref of 10 MHz???

- Int-N or Frac-N mode and why?

- Counter values?

- R x2 or div 2 yes or no?

- Feedback divider?

 

I have it setup now as an Int-N with R=100 --> Fpfd = 100 kHz, BSC divider = 2 --> Fbsc = 50 kHz, and N =24017.

No dividers or doublers enabled, loop filter designed with ADIpllSIM with ~6 kHz BW.

 

*Problem is that my phase noise is horrible.  Looking at the spectrum with a 100kHz span, I see a mound that is 10's of kHz wide around -36 dBm, far below the ~-5 dBm expected.  What I need help with is

- at what point do I switch to Frac-N mode, i.e. what Fpfd or R value?

- is the N counter the main source of my noise problems?  Of the R counter?

- ANY suggested setups would be appreciated!

 

Thanks

John

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