Hello,
Sorry for the long post, but I believe some context might be helpful:
ADL5387
Production
The ADL5387 is a broadband quadrature I/Q demodulator that covers an RF/IF input frequency range from 30 MHz to 2 GHz. With a NF = 13.2 dB, IP1dB = 12...
Datasheet
ADL5387 on Analog.com
Hello,
Sorry for the long post, but I believe some context might be helpful:
Hi,
This is because the uncertainty coming from the divider nature. When there is a divider in a path, you cannot know the output phase of the divider. For a div by 2 block, there is two different output phase state. For a div by 4 block, there is four different output phase state.
When you set RFoutB to fundamental VCO output and set RFoutA to div by 2 (assuming that you are using fundamental feedback mode), you cannot determine the output phase status of RFoutA. To mitigate the uncertainty coming from RFoutA divider, you can use divided feedback mode. In that case, the rising edge of the output divider is locked to the reference rising edge and uncertainty is mitigated. When you do that, outputs of ADF4351 are always edge aligned.
However, there is another divider in your system, ADL5387. The div by 2 block of ADL5387 creates phase uncertainty.
Below is a graphical representation of the output phase states of a div by 4 block. I hope this answers the issue that you are facing. Let me know if I miss anything.
Regards,
Kudret
Hi,
Thanks for the reply. The dividers were indeed the cause, and in the meantime has been completely fixed by choosing an equivalent mixer without LO division (ADL5382), and testing confirms the constant phase now. The explanation helped in better visualizing the problem.
Best regards
Hi,
Great explanation!
Do you know if uncertainty is eliminated if both outputs are at the same frequency with a high order division (let's say -8)? I am guessing it is by looking at this diagram, but I wanted to know if you a different point of view to it.
Thanks