Re: [Discuss-gnuradio] 8MHz Tx Bandwidth.. Nightmare and Fear

[Matt Ettus]

Vincenzo Pellegrini wrote:
> Matt,
> ...but please say it loud, say it clear: "vincenzo, you've made very big
> mistakes, because the USRP really can transmit an 8MHz wide signal
> without distorting it significantly, I've tested it"...
>   

I really don't know what you're looking for here.  There are a lot of
people transmitting a lot of different signals with the USRP and not
having issues.

There are some things you seem to be missing, though.  No system is
capable of using 100% of the nyquist bandwidth, and the USRP is no
exception.  On receive, our passband is flat out to about 75 or 80% of
nyquist.  For 8 MS/s complex sampling, that gives more than 6 MHz of
flat bandwidth.  On transmit, there are no halfband filters in there, so
you will see more rolloff from the CIC filters.  If this is a problem,
you have 3 options:

-  If your generated signal is at less than 8 MS/s complex, then you
should just upsample in software.
-  If your generated signal is at the full 8 MS/s then you can
predistort your signal to compensate for the CIC rolloff. 
-  Otherwise, I would suggest making a new FPGA image with halfband
filters in the TX side.  You can make room in there by removing one
receive chain (leaving only one).

Matt

PS  There is no need to send emails to both the list and to me.  I am on
the list, and don't need 2 copies of every email.