NI RF Phase-Coherent Multi-Channel

Hello! I would just like to ask why I'm getting the results shown in the attached file in using the NI RF Phase-Coherent Multi-Channel.
For all frequencies, I'm using the same demo program (included in NI RF Phase-Coherent Mulit-Channel) for the generation and acquisiton.
Generation: NI-RFSG Phase-Coherent Multi-Channel Generation Example
Acquisition: NI-RFSA Phase-Coherent Multi-Channel Acquisition Example
The desired results are those under the 1GHz frequency. However, I'm working on 915MHz. Needless to say, I can't see any pattern in the behavior of the plots when increasing/decreasing the frequency. That's why I really can't understand the results I'm getting.
Please help me.
Thank you very much for your time!
Attachments:
results.pdf ‏24 KB

Hello!
Attached are pictures of the hardware set-up. It is identical to the typical 2-channel phase-coherent RF signal generation and acquisition set-up.
This thread is same as http://forums.ni.com/t5/RF-Measurement-Devices/RF-Synchronization-Suite/m-p/1893713#M1995.
The software I’m using is suggested by Andy on post no.2 in the link above. I’m trying to generate a CW with 915MHz carrier frequency. However, I get incorrect plots when I use 915MHz. Setting the frequency to 1GHz results to correct plots. This is without changing any setting in the front panel.
The main problem when I use 915MHz is that one channel moves faster compared to the other channel. For example, in the IQ plot, there would be 2 points representing the 2 channels. These points travel in circular path. If the slower channel travels 1 complete circle, the faster channel is able to travel more than 1 circle. Moreover, the phase delta is not constant since one channel moves faster than the other.
More on this in the link above.
Thank you very much for your time! I really appreciate it.
Attachments:
DSC03062.JPG ‏2182 KB
DSC03063.JPG ‏1991 KB
DSC03064.JPG ‏1934 KB

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