[USRP-users] Waveform Corruption

Steve Peters stevenpeters at gmail.com
Mon Feb 27 22:00:26 EST 2012


On Mon, Feb 6, 2012 at 5:15 PM, Steve Peters <stevenpeters at gmail.com> wrote:

> I've run
>
> tx_waveforms --wave-type SINE --wave-freq=40e3 --freq=1750e6 --rate=250e3
> --ampl=0.3
>
> and at the receiver run an FFT (using the GNU Radio companion) and checked
> out the time-domain samples using my own recording & plotting tools.  I've
> also recorded the samples using rx_samples_to_file, and the result is
> similar.
>
> The results are attached.  As you can see, there are harmonics every 40
> kHz, which make the time-domain samples look pretty bad.  I've found that
> this effect gets better as the sinusoid frequency increases.  For example,
> at 100e3, the harmonics are present but are about 15 dB below the main
> sinusoid.  At 1e6, I get a pretty clean sinusoid.
>
> I've tried this in both directions (i.e., had both USRPs act as TX or RX),
> and it's the same either way.  I'm really not sure what could be causing
> this.
>
> I'm running USRP N210 with RFX1800 daughtercards.  Communication is over
> an SMA cable with 66 dB attenuation, and RX gain is set to 45 dB.
>

I just wanted to ask again about my problem, quoted above.  I'm still
observing this behavior in the RFX daughtercards, though it doesn't appear
in the BasicTX/RX cards.

Thanks again,
Steve
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