Dual RX Phase difference inconsistency

[modimo]

I tried many things to solve this. Check this thread:

RX channels alignment

Did you ever do a steady-state measurement with your system? I have found that phase is stable over a very short time, but shifts wildly over a longer period (30 seconds or more) which is trouble for me as the phase difference between the two channels shifts off of a calibrated value. Did you end up getting the sample alignment dealt with?

I calculated phase shift between channels for chirped signal (spanning over 20MHz). At each offset frequency phase shift was different(linear with frequency offset). Just as if samples were misaligned. However 1 sample shift caused to big changes. My conclusion is since ADC is sigma delta type it is possible that there would be subsample shift(since in fact ADC works at higher frequency). Resetting of the logic as was mentioned by @ricardas did not help.