[USRP-users] using tune_request_t

Sanat Gulvadi sanatgulvadi at gmail.com
Tue Jun 26 03:39:03 EDT 2012


Hi Josh,
I actually read through those pages before I emailed the list. Just want to
know if lo_offset is the variable that represents the frequency offset by
which I have to push the dc or if it's the frequency to which I want to set
the dc to.
Also is it necessary to set the policy to manual first ?
Regards, Sanat
On Jun 26, 2012 8:30 AM, "Josh Blum" <josh at ettus.com> wrote:

>
>
> 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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>
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