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.
When the new frequency exceeds the 3 GHz barrier, there is a irregularity in the phase and gain, see the figure in the attachment.
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?