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

[Marcus D. Leech]

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