2 complex receive channels on usrp n210

GNU Radio
1

Hello All,

I know that on the USRP1, it was possible to have four seperate RX
channels, and therefore receive two pairs of IQ samples. I was wondering
if
there were any way to do this on a USRP N210, using a basic RX
daughterboard, even by possible changing the FPGA code, or it you could
only have one pair of IQ samples.

Thanks,
Anisha

2

On 09/19/2012 10:44 AM, Anisha G. wrote:

Hello All,

I know that on the USRP1, it was possible to have four seperate RX
channels, and therefore receive two pairs of IQ samples. I was wondering if
there were any way to do this on a USRP N210, using a basic RX
daughterboard, even by possible changing the FPGA code, or it you could
only have one pair of IQ samples.

Yes. Same idea, except, the frontend names for Basic RX are A, B, and
AB:
http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2011-May/001271.html

-josh

3

Great! So if i selected 0:A and 0:B as multiple subdevices, I would
receive
something like I0, Q0 and I1, Q1?

4

On 09/19/2012 04:54 PM, Anisha G. wrote:

  • Frontend AB: quadrature frontend using both antennas (IQ)
  • Frontend BA: quadrature frontend using both antennas (QI)

So choosing A and B as the subdevice specs would give me two real signals,
correct?

In this case, the DDC chains will zero out Q, and connect A or B to I.
So you will get complex data centered at whatever you tune center
frequency to.

-josh

5

I am getting complex data around my center frequency, but only on one
channel, RXA shows the data, while RXB is just zeros. In my code, I have
just added a few lines from rx_samples_to_file.cpp to
rx_multi_samples.cpp
to make rx_multi_samples write out to a file. This is with the subdevice
specs A:A and A:B, should I change those?

6

I tried this out, and I am getting two real signals, while I want two
complex signals. From dboards.rst:

^^^^^^^^^^^^^^^^^^^^^^^^^^^
Basic RX and LFRX
^^^^^^^^^^^^^^^^^^^^^^^^^^^
The Basic RX and LFRX boards have 4 frontends:

  • Frontend A: real signal on antenna RXA
  • Frontend B: real signal on antenna RXB
  • Frontend AB: quadrature frontend using both antennas (IQ)
  • Frontend BA: quadrature frontend using both antennas (QI)

So choosing A and B as the subdevice specs would give me two real
signals,
correct?