On 12/14/2018 11:24 AM, Ian Buckley via USRP-users wrote:
N310 has a different ADI radio chip and since I did not work on the
design I don’t want to give you misleading advice on that one.
N210 is different, as it uses the standard Ettus interchangeable
daughter board standard. Some daughterboards have features to fully
phase align synthesizers after a retune, some not depending which
chips they are based on. UBX for example can be fully phase aligned,
but I don’t think WBX can.
I don’t recall the full product matrix as to which daughter boards
will fully align phase.
-Ian
I *think* that phase coherency across multiple N310s using common
reference and 1PPS will work, but I'm going to verify with
Ettus engineering.
There'll be the usual proviso that there won't be strict phase
alignment, mutual phase noise will be higher than with a shared-LO
approach, etc.
The N310 can accept an 2XLO input, but this has a 180deg phase
ambiguity, due to the 2X nature of the LO (The incoming LO is
at twice the desired tuned frequency, and the phase split has a 0/180
deg ambiguity).
On Dec 14, 2018, at 3:53 AM, Pablo González Fernández
<pgonza...@gradiant.org <mailto:pgonza...@gradiant.org>> wrote:
Thanks Ian. Am I correct to assume that this is not the case for
N210? What about for the N310? I am not so sure in this case, as it
uses an AD chip as the B210.
Regards
El mié., 12 dic. 2018 a las 15:26, Ian Buckley (<i...@ionconcepts.com
<mailto:i...@ionconcepts.com>>) escribió:
Brais,
Sam sent you a little bit the wrong direction there, the B200mini
has the PLL phase noise issue that precludes use in a MIMO system.
The B210 can be fully time and frequency locked to an external
10MHz reference and PPS.
What is slightly tricky about using multiple B210’s in a MIMO
configuration is that the internal frequency synthesizers will
have a residual phase ambiguity after they have been configured,
and this must be characterized and compensated for after any retune.
Watch this to gain insight into the issues involved:
https://www.analog.com/en/education/education-library/webcasts/developing-multiple-input-multiple-output.html
-Ian
On Dec 12, 2018, at 2:30 AM, Brais Ares via USRP-users
<usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>>
wrote:
Thanks Sam! If I understand correctly the link that you refer
to, it is possible to obtain time and phase synchronization with
B210s, so the only issue would be to compensate phase offset
which could be done by software. Could you elaborate a little
bit more? I'm probably missunderstading the thread you link, but
from it I take that MIMO implementations are possible with B210.
Also, can you provide any link for the difference between B210
and N210 that allows to use the later but not the former?
Regards,
Brais.
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