On 26/06/2023 11:12, Carlo Venier wrote:
Good evening to everybody,
I am trying to use an X300 with two TwinRX in a coherent setup.
After synchronization, in the case of fixed frequency operation (no
re-tuning) the phase differences among the channels are constant and
they remain constant over time.
However, if I re-tune the TwinRx on the exact same frequency, I expect
that the phase differences remain the same, but it does not happen. How
is it possible?
The LO settings are the following:
multi_usrp->set_rx_lo_export_enabled(true,
uhd::usrp::multi_usrp::ALL_LOS, 0);
multi_usrp->set_rx_lo_source("internal",
uhd::usrp::multi_usrp::ALL_LOS, 0);
multi_usrp->set_rx_lo_source("companion",
uhd::usrp::multi_usrp::ALL_LOS, 1);
multi_usrp->set_rx_lo_source("external",
uhd::usrp::multi_usrp::ALL_LOS, 2);
multi_usrp->set_rx_lo_source("external",
uhd::usrp::multi_usrp::ALL_LOS, 3);
Moreover, by using the timed command before tuning all the channels
(code snippet at "https://files.ettus.com/manual/page_sync.html";, "Align
LOs in the front-end"), I get into the issue at
("https://github.com/EttusResearch/uhd/issues/606";) and the X300 is not
usable until a power-cycle.
I get the same issues when using both the uhd3.15.0.0 and the uhd4.4.0.0.
Hopefully this bug will get fixed.
I think that without timed-tuning, even though you're sharing LOs, the
DDC phase-accumulators will be
"ticking over" between the individual (untimed) tuning commands. So
there will be unpredictable phase
between all the channels.
Should I expect the same phase differences when I re-tune to the exact
same frequency or is it okay for the phase differences to change and I
am missing something?
Do you have any suggestion on how to solve the issue?
Thanks,
Best regards,
Carlo Venier
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