[USRP-users] carrier present when transmitting zeros

Vladica Sark vladicasark at gmail.com
Wed Jul 15 12:02:06 EDT 2015


Unfortunately, I am using XCVR2450, which does not support calibration.

Does it have sense if I add some constant (DC) on top of my generated
signal?


To Carlo: What I saw in gqrx is that somehow this carrier looked quite
large. Now I checked, it is 20-25 dB difference, so, maybe it's not so
large.




On 07/15/2015 05:51 PM, mleech at ripnet.com wrote:
> There will always be *some* carrier leakage, you can reduce it by making
> sure that you've run the calibration utilities, which seek to optimize
> I/Q balance going into the mixers, and thus reduce LO leakage and image
> issues.
> 
> Along with this, you can use offset tuning, which will move the LO
> leakage outside your passband:
> 
> http://files.ettus.com/manual/page_general.html#general_tuning
> 
> Calibration notes here:
> 
> http://files.ettus.com/manual/page_calibration.html#calibration_self
> 
> In made-for-a-specific purpose radios, the final mixer also has LO
> leakage, but in a traditional superhet design, that LO leakage is
> well outside the intended passband, and generally there's a filter
> before the final RF amplifiers that removes unwanted LO leakage and
> other harmonic mixing products.  In a general-purpose, direct-conversion
> radio, that final filtering stage must necessarily be delegated to then
> end-user, since the precise filtering strategy is application and
> frequency dependent.
> 
>  
> 
>  
> 
>  
> 
> On 2015-07-15 11:44, Vladica Sark via USRP-users wrote:
> 
>> Hi there,
>>
>> I am transmitting zeros on I and Q but I can see the carrier present?
>> Anybody have idea why?
>>
>> BR,
>> Vladi
>>
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