Oops, I forgot to explain the figures. We're sending a pilot tone with a
different usrp, and split it over the 4 channels using a 4-port RF
SPLITTER. The graph shows the phase of the received signals as a
function of time (1 point every ten seconds)
Francois
16.10.2018 18:13, Marcus D. Leech via USRP-users wrote:
On 10/16/2018 07:44 AM, Francois Quitin via USRP-users wrote:
Dear all,
We encountered a small problem when we try to build a 4-element MIMO
array with two X310 (equipped with UBX daughterboards). We are
working on UHD-3.10.3:
- When we use an octoclock to provide the 10 MHz
Ref and the PPS to both X310, the phase of each receiving front-end
stays nicely constant (see octoclock.png). The Ref Source and Time
Source are set to “external” in GNU Radio (the points represent
a measurement taken every ten seconds)
- When we use the 10 MHz Ref Out and PPS Out from
one X310 and feed it to the Ref In and PPS In of the other X310, we
observe a drift in the phases of the channels from the second X310.
This is shown in the graph daisyChain.png, where we take one point
every ten seconds. We configured GNU Radio to set the Ref Source and
Time source of the first USRP to “default”, the ones of the
second USRP to “external”.
This drift is something more severe, sometimes less, but it’s
always present. Any idea why we observe this?
Many thanks,
François
What is the Y-axis scale on these plots?
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---
Francois QUITIN
Assistant Professor
BEAMS Dpt. – Embedded Electronics
Brussels School of Engineering
Université Libre de Bruxelles (ULB)
Web https://sites.google.com/site/fquitin2/
Phone +32 2 650 2829
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