[USRP-users] using tune_request_t

Josh Blum josh at ettus.com
Tue Jun 26 02:30:37 EDT 2012



On 06/25/2012 11:17 PM, Sanat Gulvadi wrote:
> Greetings,
> 
> I have a question about using the tune_request_t in my application. I have
> read from previous posts that there is an inherent DC component at the
> receiver which cannot be eliminated but can be pushed so that it occurs
> outside the band of interest.
> When I use usrp->set_rx_freq(uhd::tune_request_t(target_freq,lo_offset)) I
> am not sure what lo_offset is. I assume target_freq is the center freq to
> which I want the RF to tune to. Is lo_offset the offset by which I want to *
> push* the DC component so it ends up outside my band of interest ?


You might find helpful notes here:
http://files.ettus.com/uhd_docs/manual/html/general.html#tuning-notes

http://files.ettus.com/uhd_docs/doxygen/html/structuhd_1_1tune__request__t.html

> So in this case, if I made lo_offset say, once or twice my sampling rate,
> should this be enough to accomplish this? Do I have to additionally set the
> tuning policy to POLICY_MANUAL ?
> 

That constructor w/ the LO offset is simply a shortcut for doing this.

-josh




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