Re: [Discuss-gnuradio] Use USRP for multiple antenna application

[Matt Ettus]

Quoting Weijun Zhu <address@hidden>:

> I am interested in using the USRP to build a 4 antenna full duplex (or
> half duplex) software radio.
> The system will be pretty narrowband with probably a few tens of KHz. I
> have a couple questions as I
> am not familiar with board.

Great!

> 1. It seems that the USRP supports 2 channel readily by its design. Any
> suggestion to do 4 antennas?
>     Here is my initial thoughts.
>     Suppose I build a daughter board each contains a complete RX/TX RF
> chain (first of all, is it possible with the current daughter board
> interface?).
>     Then as long as the daughter board does real conversion instead of
> I/Q conversion, it should work, right?

This is correct.  If you do IQ you can only handle 2 antennas, but if you use
real signals you can handle 4 antennas.  Since 2 channels go to each
daughterboard slot, in order to do a 4 antenna system you would need to put 2
separate RF sections on each daughterboard.

> 2. Does the USRP support synchronization between tramisit and receive
> and between different channels.

Yes, all sampling is done completely synchronously, and there is one master
oscillator.

> 3. Any mechanism available to support cascading multiple USRPs or use
> two USRP in parallel?

Not at this time.  Each USRP does have 64 general purpose IOs which could be
used to do something like this if you wanted to develop custom FPGA designs.

> I will buy one to evaluate anyway but I appreciate any answer/suggestions.
> Thanks a lot!
> Weijun.

Great!


Thanks,
Matt