We are seeing a lot of large PFD harmonic spurs at the output of ADF4356.
When the output comes from the VCO directly (f > 3400MHz) , the harmonic spurs appear such as the picture 1. It is much larger than the datasheet.
On my eval board, f_refin = 140M, R = 2， PFD frequency is 70MHz.Fout = 6.5 GHz and 5.4GHz
Looking forward to your reply.