[USRP-users] Phase drift issue of N310

Marcus D. Leech patchvonbraun at gmail.com
Fri Mar 15 19:47:21 EDT 2019


On 03/14/2019 04:37 PM, Damon wrote:
> Hi Marcus,
>
> The UHD Version is v3.14.0.0-rc1.
>
> Best regards,
>
> Damon
>
I don't see this issue at all, using v3.14.0.0-rc3

How are you measuring phase, what does you flow-graph look like? Have 
you increased the gain enough to assure that the inherent system
   noise is not dominating your phase measurements?


>>> Hi Ali,
>>>
>>> The daughterboards have their own clock generators, but they are not
>>> exactly 'independent'. At least they don't have to be, as they share 
>>> the
>>> same reference clock. Look at the block diagram:
>>>
>>> https://kb.ettus.com/images/9/9d/USRP_N310_N300_DB_Schematic.pdf
>>>
>>> and "Ref Clock" block. I don't have N310 and I know that reality can be
>>> a bit far from expectations (i.e. look at my "What makes sense and what
>>> doesn't in the way carrier frequency is set for TwinRX currently?" 
>>> post).
>>>
>>> But maybe the daughterboards can be configured to use that reference 
>>> clock.
>>>
>>>
>>> Best Regards,
>>> Piotr Krysik
>> The LMK clock generator uses the reference clock from the mainboard, so
>> there should not be any mutual phase-jitter/drift issues.  I can test 
>> this
>>     on my N310 in the coming day or two.
>>
>> What version of UHD is in use?
>




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