[USRP-users] UBX coherence between TX and RX

Marcus Müller marcus.mueller at ettus.com
Sun Mar 24 15:07:22 EDT 2019


I can fully understand that! You don't happen to have an estimate for
that frequency offset's magnitude? Is it always the same drift? I'm
trying to narrow down analog vs numerical accuracy issues here.

Best regards,
Marcus
On Sun, 2019-03-24 at 18:39 +0000, Freedman, Michael - 1008 - MITLL
wrote:
> It is not just a phase offset. It is a frequency offset. The phase
> drifts between the two. I can tolerate a phase offset at startup. A
> freq offset however is causing problems. 
> 
> Mike
> 
> Sent from my iPhone
> 
> On Mar 24, 2019, at 4:28 AM, Marcus Müller <marcus.mueller at ettus.com>
> wrote:
> 
> Can you elaborate on what "not coherent" means to you – the relative
> phase should be constant after each tune, but if you don't tune
> simultaneously, i.e. with timed commands, random at each tune.
> 
> Best regards,
> Marcus
> On Sat, 2019-03-23 at 17:06 -0400, Michael R. Freedman via USRP-users
> wrote:
> > Hello,
> > 
> > 
> > I have an issue where I tune both the TX and RX side of a UBX40
> > card
> > in 
> > an X310 to the same frequency and find that the transmitted signal
> > and 
> > what is received are not coherent.  I am using an external 10MHz 
> > reference and have tried the documented suggestions.
> > 
> > at 150MHz it is coherent.
> > 
> > at 155MHz it is NOT coherent.
> > 
> > 
> > I have tried setting the dboard_clock_rate to 20MHz.  This made
> > the 
> > problem appear at 150MHz as well.  I've tried integer_n tuning.
> > 
> > I have verified that the ref_lock and lo_lock are both true.
> > 
> > 
> > Any suggestions?
> > 
> > 
> > Mike
> > 
> > 
> > _______________________________________________
> > USRP-users mailing list
> > USRP-users at lists.ettus.com
> > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com




More information about the USRP-users mailing list