[USRP-users] using tune_request_t

Josh Blum josh at ettus.com
Tue Jun 26 13:37:56 EDT 2012



On 06/26/2012 12:39 AM, Sanat Gulvadi wrote:
> 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.

The constructor with the lo_offset will do exactly this.

> Also is it necessary to set the policy to manual first ?

No, the constructor with lo_offset sets this automatically.

-josh

> 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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>> USRP-users at lists.ettus.com
>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>
> 





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