[USRP-users] carrier present when transmitting zeros

mleech at ripnet.com mleech at ripnet.com
Wed Jul 15 11:51:23 EDT 2015


 

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
> 
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com [1]
 

Links:
------
[1] http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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