[USRP-users] TX and RX paths sharing a coherent LO

Marcus Müller marcus.mueller at ettus.com
Wed Oct 8 13:19:54 EDT 2014


No, the LOs used for mixing are individually generated from the same
10MHz reference; they thus don't drift away from each other, but they
don't share the same jitter etc. However, the Ettus daughterboards
usually use rather decent synths, and thus the LO quality should be
dominated by the quality of the reference clock -- which again, is quite
ok, for most applications, and can be further optimized by
GPS-disciplining the reference.

Usually, that's how close you can get to shared LO if you want
independent TX and RX mixers.

Greetings,
Marcus

On 08.10.2014 19:04, Rickard Radio via USRP-users wrote:
> Sounds good!
>
> Does this mean it really shares the same LO, i.e., also with the same and
> uniquely occurring phase noise shared to all paths?! (I want that!)
>
> Regards,
> Rickard
>
>
>
> On Wed, Oct 8, 2014 at 6:54 PM, Marcus Müller <usrp-users at lists.ettus.com>
> wrote:
>
>>  Hi Rickard,
>>
>> all the LOs are synthesized from the same motherboard reference, so Q1 is
>> answered with "you get that for free".
>> Q2 is "yes".
>> Q3 gets the answer "if you want to use definite times when sampling, use
>> the timed commands feature of UHD".
>> :)
>>
>> Greetings,
>> Marcus
>>
>> On 08.10.2014 18:48, Rickard Radio via USRP-users wrote:
>>
>> Dear usrp-users,
>>
>> I am interested in coherently LO-mixing different TX and RX paths for some
>> experiments.
>>
>> Q1: Which options exist to use the same(?) coherent(!) LO for different TX
>> and RX paths on the USRPs (N210 and/or B210)?
>> Q2: Related, with the N210s and the MIMO cable, can I obtain and use a
>> coherently shared LO for different TX and RX paths?
>> Q3: Follow up  - do I need something else or in addition ?
>>
>> Regards,
>> Rickard
>>
>>
>>
>>
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>
>
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