On 05/09/2018 06:53 PM, Jacob Knoles via USRP-users wrote:
Hello All,
I am trying to generate OFDM signals of various bandwidths using the
X300 (UBX-160), particularly 20/40/80 and 160 MHz bandwidths.
I have used the gnuradio ofdm_tx.grc example file to generate a data
file which I then feed into the USRP an monitor on a spectrum analyzer.
To quickly note, I do not care about the data being transferred, it
will not be received or demodulated in any way and is simply an
interfering signal.
At this time I can produce a 20 MHz wide OFDM signal as well as a 100
MHz wide signal (?) but the 40/80 MHz signals are rounded and look
more like an 802.11b signal.
I have noted a message from the X300 that the requested sample rates
(40/80 MS respectively) cannot be achieved due to the 200/x ratio
being odd.
So my question is this, how do I decouple the USRP's sample rate with
the bandwidth of the signal I am trying to produce?
To put it another way, I produce a data file at 40 MS/s rate then run
it on the X300 at 100 MS/s and I get a 100 MHz wide signal instead of
the 40 MHz I want.
Thanks for the help.
-----------------------------
Jacob Knoles
You would need to interpolate it up to the desired rate. UHD has no way
of knowing that your samples represent data sampled at 40Msps, so when you
pull it out of your file at 100Msps, it will get presented as if it
were 100Msps data.
You'll need to use some DSP code, or Gnu Radio to up-sample your sample
file.
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