[USRP-users] spectral leakage ?!

James Humphries james.humphries at ettus.com
Fri Oct 2 09:55:13 EDT 2015


Some LO leakage is typical with the system. When you say sometimes not
necessarily at the center frequency, how far away from center is it?

-Trip

On Thu, Oct 1, 2015 at 7:53 AM, Amina M. Fellan via USRP-users <
usrp-users at lists.ettus.com> wrote:

> Hello everybody !
>
> I'm using 2 USRPs N210 equipped with SBX daughterboards with GNU Radio to
> establish BPSK communication over ISM band. For the latter, I started with
> the benchmark_tx/_rx.py examples.
>
> currently I'm trying to measure the SNR at the receiver. I tried using the
> SNR estimation blocks in the GRC but they seem to be giving erroneous
> readings, so I decided to try with a spectrum analyzer to estimate the SNR
> using (S+N)/N.
>
> I noticed that even when there's no transmission going on, so trying to
> measure the noise floor, a signal appears on the spectrum and sometimes
> even not necessarily at the center frequency. This also can be seen using
> the uhd_fft script from GNU Radio. Attached is a photo of how the spectrum
> looks if the USRP is on without transmitting/receiving !!
>
> Any clues what is causing this problem ??
>
> Thanks for your time !
>
> Cheers,
> Amina
>
>
>
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>
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