Im trying to learn/understand how this spurs get generated. So maybe someone here can try to explain.
I have ADF4351 with PDF=32MHz (max for frac-n mode). For example at 550.006MHz i get spurs every 4kHz.
In this example i have PFD=32MHz, INT=68, FRAC=3003, MOD=4000, OutDIV=4, channel spacing is 0,002MHz.
At same frequency 550,006, if i set R=2, so PFD=16MHz, INT=137, FRAC=1003, MOD=2000, they dissapear.
Is there any formula, i can calculate how they are generated or predict where i can expect them in whole frequency range with PFD=32MHz or any info on what kind of spurs are there and how are they generated inside of the chip?
Look at attached images. Last image is example at 550.002MHz with PDF=32MHz.