Re: [Discuss-gnuradio] Odd use of LO phase lock feature on USRP for RFID application

[Matt Ettus]

On 04/19/2011 11:38 AM, Colby Boyer wrote:
> Hi All,
> 
> In RFID applications, a reader receives (backscatter from RFID tag) and
> transmits (constant tone) at the same frequency. With commercial
> readers, a single LO will be shared by the RX and TX chain. However, in
> the USRP case, two separate daughter boards are used so different LOs
> are in use for the RX and TX chain. So you should end up with some
> frequency offset in RX chain due to mismatched clocks.
> 
> Is it possible to lock the LOs of a TX daughter board and a RX daughter
> board, as you would for a traditional MIMO 2 TX or 2 RX setup? There
> appears to numerous discussions and examples of the latter. I'm thinking
> it would be possible. But I'm more of a systems guy and less of a RF
> hardware guy, so any comments would be appreciated.
> 
> Thanks,
> Colby


As long as you set them to the same frequency, they're already locked.
No need to do anything different.

Matt