Re: [Discuss-gnuradio] USRP inserts a peak in the carrier frequency

[frankist]

Oops. problem solved. I had to increase the LO offset in the transmitter (not
the receiver)! *Facepalm*

Thanks for the support


mleech wrote:
> 
> On 07/04/12 10:12 AM, frankist wrote:
>> Hi,
>>
>> I am using GNU Radio for 2 weeks. I always get in the receiver side a
>> signal
>> with a peak in the carrier frequency when I turn on the transmitter even
>> if
>> I send a signal made of zeros. You can see it in the picture 
>> http://old.nabble.com/file/p33648622/usrp_carrier_peak.png 
>>
>> In spite of being handy to discover the frequency offset of my signal, it
>> is
>> influencing my results when I try to measure the power of the received
>> signal. I thought this was the DC offset, but I read somewhere that USRP2
>> eliminates the DC Offset.
>>
>> So, do you know what it is and how to remove it?
>>   
> This is LO leakage. What is you setup here--two USRPs with XCVR cards?
> 
> Mixers always have some amount of LO leakage at the output port. 
> Depending on your signal bandwidth,
>  you can use an LO offset to move that leakage outside of your
> applications passband, but there'll still be
>  leakage--just not at a place that matters to you.
> 
> -- 
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortium
> http://www.sbrac.org
> 
> 
> 
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> 

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