[USRP-users] UBX coherence between TX and RX

Michael R. Freedman mfreedman at ll.mit.edu
Mon Mar 25 06:22:40 EDT 2019


Marcus,


Thanks for engaging in this.  I will have frequency deltas for you first 
thing this afternoon.


Mike


On 03/24/2019 03:07 PM, Marcus Müller wrote:
> 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
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