May I get 2 receivers on same channel by one USRP2?

GNU Radio
1

hi,

Now I am working with BasicRX daughterboard. I want to implement
multi-receivers on the same channel. It works well when I connect only
one antenna to RX-A of BasicRX borad.Then I want to sample by 2
antennas,which connect to RX-A and RX-B on BasicRX board. What
configuration should I change? Is the data interleaved in this case?

Thanks for your help!

Liang

2

On Tue, Jul 21, 2009 at 06:44:26PM +0800, 周亮 wrote:

hi,

Now I am working with BasicRX daughterboard. I want to implement
multi-receivers on the same channel. It works well when I connect
only one antenna to RX-A of BasicRX borad.Then I want to sample by 2
antennas,which connect to RX-A and RX-B on BasicRX board. What
configuration should I change? Is the data interleaved in this
case?

The data is interleaved.

Please look in gnuradio-examples/python/multi-antenna. Those examples
work with 4 antennas using 2 Basic RX’s. Your case is a subset of
what those examples demonstrate.

Eric

3

Please look in gnuradio-examples/python/multi-antenna. Those examples
work with 4 antennas using 2 Basic RX’s. Your case is a subset of
what those examples demonstrate.

Don’t all of the multi-antenna files require a specific FPGA build
(ie, unique to the USRP1) to get two real signals from a single
daughterboard? Is there such an FPGA build for the USRP2? (I ask
because the multi-antenna scripts don’t seem to represent that)

Jason

4

On Tue, Jul 21, 2009 at 11:48, Jason U.[email protected] wrote:

Don’t all of the multi-antenna files require a specific FPGA build
(ie, unique to the USRP1) to get two real signals from a single
daughterboard? Is there such an FPGA build for the USRP2? (I ask
because the multi-antenna scripts don’t seem to represent that)

The current USRP2 FPGA build treats the Basic/LFRX as I and Q baseband
cards, with a single DDC for frequency conversion and sample rate
conversion, resulting in a single IQ stream over the GbE.

It is possible to write an FPGA image with 2 DDCs that have TX_A and
TX_B connectors routed individually as I channels (with Q set to 0.)
However, the current host interface does not provide a way to
independently set two different DDC parameters (frequency and
decimation) or to receive two sample streams.

Long term, this will get fixed when we have the VRT interface in release
3.3.

Short term, there will be an alternate FPGA build that does the above,
but the two DDCs will share conversion frequency and decimation, and
will result in an interleaved I1Q1I2Q2 type stream. This would at
least allow coherently sampling two baseband inputs.

Johnathan

5

On Tue, Jul 21, 2009 at 12:38, Johnathan
Corgan[email protected] wrote:

It is possible to write an FPGA image with 2 DDCs that have TX_A and
TX_B connectors routed individually as I channels (with Q set to 0.)

Uh, that would be RX_A and RX_B…

Johnathan

6

On Tue, Jul 21, 2009 at 01:48:22PM -0500, Jason U. wrote:

Please look in gnuradio-examples/python/multi-antenna. Those examples
work with 4 antennas using 2 Basic RX’s. Your case is a subset of
what those examples demonstrate.

Don’t all of the multi-antenna files require a specific FPGA build
(ie, unique to the USRP1) to get two real signals from a single
daughterboard?

Note: I missed the USRP2 part in the subject on my first reply…

On the USRP1, they do if you want the 4 Rx chains. The standard FPGA
image for the USRP1 contains 2 Rx and 2 Tx chains, so (if he was using
the USRP1 (which he isn’t)) he could do two Rx with the standard image.

Is there such an FPGA build for the USRP2? (I ask
because the multi-antenna scripts don’t seem to represent that)

Right now the standard USRP2 FPGA image contains a single Rx and
single Tx chain. Once the conversion to VRT is done (and we overhaul
the API so that you can control a wide variety of things such as
multiple Tx and Rx chains), this will be possible on the USRP2.
In the meanwhile, folks are on their own :wink:

Eric