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

Josh Blum josh at ettus.com
Fri Jun 29 18:04:14 EDT 2012



On 06/29/2012 03:00 PM, Josh Blum wrote:
> 
> 
> 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
> 

And some additional links about XCVR2450 properties:
http://files.ettus.com/uhd_docs/manual/html/dboards.html#xcvr-2450

And some helpful explanation about the two stage tuning:
http://files.ettus.com/uhd_docs/manual/html/general.html#tuning-notes

Cheers!
-josh




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