[USRP-users] tunnel.py doesn't receive packages when transmit and receive frequencies are different

Josh Blum josh at ettus.com
Fri Jun 29 18:00:28 EDT 2012



On 06/29/2012 02:58 PM, Li Sun wrote:
> But can we set one daughter board's RX and TX at different frequency, e.g.
> RX at 2.412GHz, TX at 2.432GHz ?
> 

Yes, it is possible to have two different center frequencies for
XCVR2450 RX and TX. The only requirement is that the RF frontend is
tuned to the same frequency for TX and RX. However, the DSPs can be used
to shift the signal digitally as long as you remain with the bandwidth
of the daughterboard.

So, to so this: You can use the tune_request_t to ask for a desired
center frequency, but enforce a specific RF frequency.
1) create a tune request with the desired center frequency
2) set rf_freq to the desired LO frequency
3) set rf_freq_policy to MANUAL.

Note: tunnel.py does not have a command line option for this level of
control. So you will need to modify the gnuradio example to implement this.

Some doxygen here for tune request:
http://files.ettus.com/uhd_docs/doxygen/html/structuhd_1_1tune__request__t.html

-Josh




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