artiq phase noise consultation

[zhouyabin]

I used a low phase noise signal source as my artiq frequency reference，The reference frequency is 100MHz


this source looks relatively clean.
But my artiq DDS output frequency produces some other unknown noise besides the sidebands. And his phase noise curve is not very good


He looks bad, the frequency of the output produces other noise besides the sidebands.
Below is the frequency output and phase noise curve using artiq internal clock reference


After artiq connects the external clean source as the frequency reference, the phase noise curve should be better, but it doesn't seem to be, I don't know how to solve this problem, thank you all.

[gkasprow]

Can you describe the setup you are testing?

[gkasprow]

I tested early versions of Urukul and no such effects were observed. Due to component shortages we replaced some parts and it's quite possible that it caused the issue.

[aewallin]

FWIW here is some phase-noise data (from 2022) from our Urukul (AD9912) at ca 25 MHz output. This is measured with a Microsemi 3120A phase-noise-probe, so the max measurement frequency is 30MHz. The reference-frequency for ARTIQ and the phase-noise-probe comes from the same source (Hydrogen maser) via a distribution amplifier.