Can our USRP do this? --Help really needed from fellows gnur

GNU Radio
1

Hi everybody,

I guess I’m doing something wrong with how I use my USRP but I really
need someone to confirm that a signal like the one in the attached
picture can be transmitted with USRP+BasicTX (or even another board),
before I dive into finding the mistake.

So Has someone ever verified he’s able to transmit an 8 Mhz Wide (7
without the virtual carriers) complex signal like the one shown?

Or could anybody be so stupendously kind to try to send this gr_complex
data dump (usrp_interp = 16)

http://wwvince.interfree.it/of.dump

towards a good spectrum analizer ( I don’t have one… :frowning: )
and send me back a picture of the result on the screen?

this would be a huge help to ma thesis work… :smiley:

thanks thanks thanks

vincenzo

PS.
Matt, can you confirm that what I’m asking is within the USRP’s reach?
the center frequency I’m using is 212.5MHz with Basic TX, but I keep
getting unreasonable outputs…

PS2.
I know I’m asking much… but if someone were willing to lend me a
hand…

2

Hi!

If you experience strong distortions in your signal, then this could be
related to the cic interpolator and decimator in the usrp. I am
transmitting ofdm signals. When those signals occupy the whole sample
bandwidth, or a greater part of it, the frequency band at the border is
greatly attenuated. Especially when the complete bandwidth is used (i.e.
in your case 8 Mhz), the received signal looks similar to a gaussian
distribution.

At the moment, I bypass this problem by using filters on transmission
and receiving side. They interpolate/decimate by a constant factor, for
example 2x. The data rate sent to usrp is therefore doubled.

To test the filter and run some experiments, I have modified usrp_fft.py
and usrp_siggen.py. Maybe you want to have a look at these.

My hardware are two usrp’s, revision 4.2, with Flex2400 daughterboard
installed.

Greetings
Dominik