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Gain/Phase Jump at Divider Change

Question asked by fischer on Oct 16, 2017
Latest reply on Oct 25, 2017 by sripad

We use the AD9361 in a own designed PCB and have connected the TX output with the TX monitor input over some external passive circuits.
Now we do a frequency sweep from 2,8 GHz to 3,156 GHz with 39 steps and a step width of 8,9 MHz.
In the IQ Plot we see the phase change over frequency, see the figure in the attachment.
Our problem:
When the new frequency exceeds the 3 GHz barrier, there is a irregularity in the phase and gain, see the figure in the attachment.

Our assumption:
The VCO jumps from 12 GHz to 6 GHz when the frequency is over the 3 GHz and the divider changes.  
The gain over frequency is not the same for this two VCO frequency interval limits. Is this a correct assumption?
In the data-sheet there are no gain over frequency figures for a frequency interval with divider change. Is there a figure available over the whole frequency range of the AD361?