Hi, folks.In application note from Ettus, "Synchronization and MIMO Capability with USRP Devices",They said that "Generally, these fractional-N synthesizers introduce a random phase offset after each retune."What does "random phase offset" mean?Q1. Does it mean that if I send a signal, Acos(fc*t), then It actually sends the signal Acos(fc*t + "random phase")?Q2. After retuning, unless I retune it again, does the random phase offset retain consistently?Am I correct?Thanks in advance.Regards,

On 03/07/2018 12:04 PM, Hojoon Yang via USRP-users wrote: > > Hi, folks. > > In application note from Ettus, "Synchronization and MIMO Capability > with USRP Devices", > > They said that "Generally, these fractional-N synthesizers introduce a > random phase offset after each retune." > > What does "random phase offset" mean? > > Q1. Does it mean that if I send a signal, Acos(fc*t), then It actually > sends the signal Acos(fc*t + "random phase")? > It means that if you have two receivers that are otherwise synchronized (via shared reference clock, and time-aligned via 1PPS), each receiving the same, otherwise-phase-aligned, signal, the two receivers will see the signal with different phase offsets, because the two (or more) LOs are not running at exactly the same phase offset. > > Q2. After retuning, unless I retune it again, does the random phase > offset retain consistently? > Indeed, provided that all the receivers involved are sharing a 10Mhz reference clock, and are time-synchronized, the phase offset will remain more-or-less constant throughout a given "run". I say more-or-less because there is analog circuitry involved and very-fine-scale group delays will shift randomly in different directions in the two pieces of hardware, but this should be very small. > Am I correct? > > Thanks in advance. > > Regards, > > > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com