Hi, there. Use the 25 MHz reference frequency that comes with the ADF4351 evaluation board, and the output frequency is 1422 MHz. The parameter design is shown in the figure below: Using the output frequency of the spectrum analyzer, Span is set to 100 Hz, VBW and RBW are automatically set, and the frequency is found to randomly jump within a range of tens of Hz near 1422 MHz. Excuse me, what is the frequency resolution of the ADF4351? Can the ADF4355-3 solve the problem? Thanks for the answer.