Hi,
I have an eight element circular antenna array and I want to do
beamforming
using eight N210s in receive mode. So, I distributed 10MHz/1PPS
reference to
each N210 to synchronized them and routed the eight GbE ports through a
switch to the computer. I store data from each channel in one
file/channel
using gnuradio companion. Later I want to do beamforming processing.
Now, when I start receiving the data, there is a fixed phase offset from
channel to channel. That’s OK as long as I know how much is it. The
problem
I am facing is that this phase offset is random each time you start
acquiring the data. Now how can i know about it to make a correction in
the
array processing. Is there a way to fix it or take care of it in system
calibration?
Thanks,
Khalid.
Could you post a screen shot of the flow graph or attach the grc file?
-Josh
The GRC file is attached. Here i am showing it scope sink with six
channels.
Khalid.
Josh B. wrote in post #994831:
Could you post a screen shot of the flow graph or attach the grc file?
-Josh
Hi,
I was building an 8-channel system using N210s. I got a 10MHz/1PPS OCXO
clock from jackson labs and applied it across all channels. The result
is
that all channels got phase-locked but still with a random phase offset
between channel-to-channel. The bad thing is that this phase offset is
random every time you tune or re-tune the system. The reason being, what
I
understood, that we are not distributing the same LO across all N210s
but
asking their freq synthesizers to PLL to a 10MHz freq reference. This is
not
the best way to achieve a phase coherent system anyway. The best thing
would’a been to daisy-chain a single LO across all usrps but that’s not
the
case here.
So, now I am trying is to build my own calibration mechanism by
injecting a
known phase at each channel before acquiring the actual signals without
re-tuning the system. I hope it will do the job. At least the first
attempt
was encouraging. HIH.
Khalid.
On Wed, Jun 22, 2011 at 5:38 PM, Scott Johnston