[USRP-users] UBX coherence between TX and RX

Freedman, Michael - 1008 - MITLL mfreedman at ll.mit.edu
Sun Mar 24 14:39:05 EDT 2019


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
> 
> 
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