[USRP-users] UBX coherence between TX and RX

Marcus D. Leech patchvonbraun at gmail.com
Sun Mar 24 15:23:46 EDT 2019


On 03/24/2019 02:39 PM, Freedman, Michael - 1008 - MITLL via USRP-users 
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
Also, what version of UHD?  What hardware rev of UBX cards?


> 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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>
>
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