[USRP-users] carrier present when transmitting zeros

mleech at ripnet.com mleech at ripnet.com
Wed Jul 15 12:09:04 EDT 2015


 

Adding DC to your baseband signal will make the problem worse. 

On 2015-07-15 12:02, Vladica Sark via USRP-users wrote: 

> 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 [1] Calibration notes here: http://files.ettus.com/manual/page_calibration.html#calibration_self [2] 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 <mailto:USRP-users at lists.ettus.com> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com [3]

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Links:
------
[1] http://files.ettus.com/manual/page_general.html#general_tuning
[2] http://files.ettus.com/manual/page_calibration.html#calibration_self
[3] http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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