Hi Marcus, I have one more question, SBX and UBX support phase alignment (phase synchronization) on certain usrps. Does phase alignment means that after using timed commands, the phase offset between two front-ends will be always zero (or very close to zero) or just be a constant which doesn't vary when we re-tune. I observed that even if we don't use the timed commands, the phase offset will be fixed after tuning but the offset value is different for different runs, so I feel confused about the term 'phase alignment'.
Thanks a lot! Best Yang On Wed, Jan 9, 2019 at 9:19 PM Marcus D. Leech <patchvonbr...@gmail.com> wrote: > On 01/09/2019 08:54 PM, Yang Liu wrote: > > Hi Marcus, > > Thanks! > > I feel a little confused about the term 'frequency synchronization'. if > the two LOs on the two daughterboads are using the same frequency > reference, does it mean that after tuning, they will produce identical > CFOs to the same receiver (one receiving channel) or we can say that the > difference in CFOs are almost negligible? (lets for now ignore other > factors that can contribute to CFO) > I read through 'align LOs in the front-end' in the link > https://files.ettus.com/manual/page_sync.html. timed command makes sure > that different daughterboads can be tuned at the same time, so that it can > only help to mitigate the phase offset, but it doesn't say anything about > the potential frequency offset between the two daughterboards. > > Best, > Yang > > There will be no frequency offset between the two cards--they're > programmed identically, and use the same reference clock. So other than > phase-noise and phase-offset, they will be, for all intents, "identical". > > > > > On Wed, Jan 9, 2019 at 3:17 PM Marcus D Leech <patchvonbr...@gmail.com> > wrote: > >> Yes they’ll use the same reference clock provided by the motherboard. >> >> There’ll be a residual phase offset which can be mitigated using timed >> tuning. >> >> Sent from my iPhone >> >> > On Jan 9, 2019, at 3:01 PM, Yang Liu via USRP-users < >> usrp-users@lists.ettus.com> wrote: >> > >> > Dear all, >> > >> > I have a usrp x310 with two UBXs installed. And I want to use it as a >> MIMO transmitter (two outgoing channels streaming at the same frequency). >> > >> > When we need to build a MIMO system by connecting different usrps, I >> know that we need to have either MIMO cable or external time and frequency >> reference. In the one usrp x310 case, since two daughterboards seems to be >> independent, do we need to synchronize them? or they are already >> synchronized by default (for example, two local oscillators are >> synchronized, and will be tuned to exactly same frequency?)? >> > >> > Thanks, >> > Yang >> > _______________________________________________ >> > USRP-users mailing list >> > USRP-users@lists.ettus.com >> > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> > >
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