I'm using the programming software supplied for the ADF4159 evaluation board - Revision 4.9.0 dated October 2013 and find that it seems to generate incorrect register values for certain frequencies. In my example cases it seems to generate frequencies that are approximately 20kHz too low from what I requested. If I increment the requested frequency by the smallest possible step the correct frequency is generated. Please see the attached screen shot of the GUI. Rather confusingly the software generates incorrect register values when requested frequencies are at or near integer boundaries, so of course an integer boundary spur is seen at the desired frequency. So the software has an integer boundary problem as well as the hardware! Our software engineers have easily fixed the software problem (something to do with floating point conversion ......) - if only we could fix integer boundary spurs in the hardware!
As a thank you for pointing out errors in ADI code, perhaps ADI could send us an evaluation board for their latest fractional N PLL with integrated VCO the ADF4355 ?