[USRP-users] using tune_request_t

Josh Blum josh at ettus.com
Wed Jun 27 13:07:12 EDT 2012



On 06/27/2012 05:52 AM, Sanat Gulvadi wrote:
> Hi Josh,
> 
> I'm sorry for asking again. But could you please tell me if the following
> line will help push out the dc component outside my band.
> usrp->set_rx_freq(uhd::tune_request_t(2.44e9,100e6/32));
> Here I am trying to tune to 2.44 GHz and my sampling rate is 100e6/64.
> Should this work ?
> 

That looks correct.

-josh

> Regards,
> Sanat
> 
> On Tue, Jun 26, 2012 at 7:37 PM, Josh Blum <josh at ettus.com> wrote:
> 
>>
>>
>> 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
>>>>
>>>> _______________________________________________
>>>> USRP-users mailing list
>>>> USRP-users at lists.ettus.com
>>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>>>
>>>
>>
>>
> 





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