I am using ADF4351 to make a wave generator with the range of 500MHz to 2.5GHz. I purchased a clone board from eBay, and I drove the board with Arduino. When I used the board to generate single frequency, the single looks fine on the spectrum diagram. However, when I doing the sweep, lots noise peaks coming out. It seems like harmonic peak, but I doubt it could also be the frequency leaking from the VCO or divider. And some noise peak even went up to 5dBm lower than the single, that made it worse. I am wondering where are those noise peaks coming from? And is there any way that I can eliminate those noises? Or is that possible that I bought a fake chip? Does the official eval board have a better sweeping performance? Really appreciate!